A firm’s marginal revenue and marginal cost functions are given by
MR = 140 − 6Q and MC = Q2 + Q + 20
Fixed costs are 10.
(a) Write down an expression for total revenue and deduce the corresponding demand function.
(b) Write down an expression for the total cost function.
(c) Find the value of Q which maximises profit, π, and state the corresponding value of π.