p= Q-Rx, where Q and R constants.

A tax of Rs.K per unit is levied by the government. The manufacturer adds the tax to his cost.

(a) find the price and the output both before and after tax.

(b) show that the tax brings in maximum return when K=(Q-b)/2

I could solve the 1st question i.e. (a). But I don't know how to solve (b). Please help.