How to set SQL server name while install it programatically?

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SQL

psi.Arguments = "/qb username=\"sa\" companyname=\"Rumtek\" addlocal=ALL  disablenetworkprotocols=\"0\" instancename=\"SQLExpress\" SECURITYMODE=\"SQL\" SAPWD=\"lock\"";
            p.StartInfo = psi;
            p.Start();

i have tried the above code which helps me to install SQL Express; but SQL automatically set its SERVER name as per the Computer Default Name.
How do i set the SERVER name through passing parameter?