Q. Marginal revenue is equal to market prevailing price). Prevailing market price of lawn mowing is $20 per acre. Although John can use family mower for free, he has or costs given by: T C = 0.1Q2 + 10Q + 50 (1) where Q is number of acres John chooses to mow in a week. How many acres should John choose to mow in order to maximize profit?