Service tax on purchase order amount

sanjiv (Admin) (96 Points)

27 December 2011  

"A" is a manufacturer, it has excise registration for manufacturer, service tax registration for GTA and business auxiliary service, now "A" makes a rolling machine, and also does the erection, installation, commissionig of these machine at the buyers site. Now say the  Amount of purchase order is 1000000 (which includes supply of machines, and above mentioned services), but the cost of goods supplied is say 700000. In the purchase order the scope of work includes erection, installation etc. 

Now what i want to know is "A" liable to pay service tax on (1000000-700000)=300000 as works contract service provider at the rate of 4% or 10%?