Suppose Kate's Great Crete (KGC)has Annual Variable Costs of VC

Suppose Kate's Great Crete (KGC) has annual variable costs of VC = 30Q + 0.0025Q² and marginal costs of MC = 30 + 0.005Q,where Q is the number of cubic yards of concrete it produces per year.In addition,it has an avoidable fixed cost of $50,000 per year.KGC's demand function is Q^d = 20,000 - 400P.What is the profit maximizing sales quantity?

A) 20
B) 2,000
C) 8,000
D) 0