drawing lines in a bitmap which is inserted in picturebox using c#

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C#

I have taken a form which consits of listbox and a picturebox witha bitmap.
when i click a button...an action is performed which is called createbitmapatruntime();

at that time the bitmap is white in colour with x and y axis...and on mouse move we can c the coordinates....at the placed mouse pointer.

i have another button...which when triggered...fills the listbox with filesizes(suppose 20 files)..
of a particular folder.

size of bit map is 800*600.

all the filessizes which are in MB is converted to bytes.

now /...i want to plot different file sizes for each iteration on x axis.

suppose origibnal file size is 500...and rest file sizes are less than 500...

x axiz will be 10 parts...each part representing 80 points.

1ST file coordiante(80,500)
2nd file cordinate(160,480)...

3rd file coordinate(240,460)....and so on...how should i mark points...and then draw a line or curve using these points.