i've developed a code for producing a report based on the given values by using some formulae.,but i'm getting some errors.i'm posting my code.,please check that and solve the issue

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C#

below are the formulae., to use in the code
Criteria:

% Down Time : (down time / 8*date diff)*100

Average % Down Time by no of complaints : Sum of % down time / no of complaints

Average % Down Time by no of System under AMC : (Sum of Down time for 8hrs / 4000*90*8) * 100

% of complaints taken more than 3 days:(No of complaints More Than 2 days/Total No of complaints)*100

public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        string assign = Session["assignee"].ToString();
        string sda = Session["sdate"].ToString();
        string eda = Session["edate"].ToString();
        string gd = Session["gdt"].ToString();
        string ld = Session["ldt"].ToString();

        # region sqlconnection
        //SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["kaseyaConnectionString3"].ConnectionString);
         //string select = "select str((SUM([percent])/count([percent])),7,2) from Datediff$ where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
         SqlCommand cmd = new SqlCommand();
         cmd.Connection = con;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = select;
         con.Open();
         Label1.Text = cmd.ExecuteScalar().ToString();
         con.Close();

         string select2 = "select str(((SUM([Calculated(on time)])/(4000*90*8))*100),7,2) from Datediff$ where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
         SqlCommand cmd2 = new SqlCommand();
         cmd2.Connection = con;
         cmd2.CommandType = CommandType.Text;
         cmd2.CommandText = select2;
         con.Open();
         Label2.Text = cmd2.ExecuteScalar().ToString();
         con.Close();


         string select3 = "select max([Calculated(on time)]) from Datediff$  where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "' and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
         SqlCommand cmd3 = new SqlCommand();
         cmd3.Connection = con;
         cmd3.CommandType = CommandType.Text;
         cmd3.CommandText = select3;
         con.Open();
         Label3.Text = cmd3.ExecuteScalar().ToString();
         con.Close();


         string select4 = "select min([Calculated(on time)]) from Datediff$  where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
         SqlCommand cmd4 = new SqlCommand();
         cmd4.Connection = con;
         cmd4.CommandType = CommandType.Text;
         cmd4.CommandText = select4;
         con.Open();
         Label4.Text = cmd4.ExecuteScalar().ToString();
         con.Close();


         string select5 = "select min([percent]) from Datediff$   where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "' AND [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
        // string select5 = "select str(((cast(c.a as float)/cast(d.b as float))*100),7,2)  from  (select COUNT(Time_diff) a  from datediff$ n where n.Time_diff>72 and [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "' and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "') c,(select COUNT(Time_diff) b from datediff$ where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "') d";

        //SqlCommand cmd5 = new SqlCommand();
        // cmd5.Connection = con;
        // cmd5.CommandType = CommandType.Text;
        // cmd5.CommandText = select5;
        // con.Open();
        // Label5.Text = cmd5.ExecuteScalar().ToString();
        // con.Close();
        #endregion
        OleDbConnection con = new OleDbConnection("provider=microsoft.jet.oledb.4.0;Data source=E:\\downtime2\\App_Data\\datediff$.mdb");
        //str((SUM([percent])/count([percent])),7,2)

        string str = "select str((SUM([Calculated(on time)])/count([Calculated(on time)])),7,2) from datediff$ where Assignee = '" + assign + "' and [Creation_date] >='" + sda + "' and [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' and [Calculated(on time)] <= '" + ld + "' ";
      //string str =  "select * from datediff$ where Assignee = '" + assign + "'";
      //  string str = "select sum([id1])/count([id1]) from calculation where id1 between'" + sda + "' and '" + eda + "'";
        OleDbCommand cmd = new OleDbCommand();
        cmd.Connection = con;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = str;
        con.Open();
        //OleDbDataReader dr = cmd.ExecuteReader();
       Label1.Text = cmd.ExecuteScalar().ToString();
       //cmd.ExecuteNonQuery().ToString();
        //Label1.Text = assign;
        con.Close();

        string select2 = "select str(((SUM([Calculated(on time)])/(4000*90*8))*100),7,2) from datediff$ where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
        OleDbCommand cmd2 = new OleDbCommand();
        cmd2.Connection = con;
        cmd2.CommandType = CommandType.Text;
        cmd2.CommandText = select2;
        con.Open();
        Label2.Text = cmd2.ExecuteScalar().ToString();
        con.Close();


        string select3 = "select max([Calculated(on time)]) from datediff$  where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "' and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
        OleDbCommand cmd3 = new OleDbCommand();
        cmd3.Connection = con;
        cmd3.CommandType = CommandType.Text;
        cmd3.CommandText = select3;
        con.Open();
        Label3.Text = cmd3.ExecuteScalar().ToString();
        con.Close();


        string select4 = "select min([Calculated(on time)]) from datediff$  where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
        OleDbCommand cmd4 = new OleDbCommand();
        cmd4.Connection = con;
        cmd4.CommandType = CommandType.Text;
        cmd4.CommandText = select4;
        con.Open();
        Label4.Text = cmd4.ExecuteScalar().ToString();
        con.Close();


        // string select5 = "select min([percent]) from Datediff$   where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "' AND [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "' ";
        string select5 = "select str(((cast(c.a as float)/cast(d.b as float))*100),7,2)  from  (select COUNT(Time_diff) a  from datediff$ n where n.Time_diff>72 and [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "' and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "') c,(select COUNT(Time_diff) b from datediff$ where [Assignee] = '" + assign + "' AND [Creation_date] >='" + sda + "' AND [Creation_date] <= '" + eda + "'  and [Calculated(on time)] >= '" + gd + "' AND [Calculated(on time)] <= '" + ld + "') d";
        OleDbCommand cmd5 = new OleDbCommand();
        cmd5.Connection = con;
        cmd5.CommandType = CommandType.Text;
        cmd5.CommandText = select5;
        con.Open();
        Label5.Text = cmd5.ExecuteScalar().ToString();
        con.Close();
    }
}