A math function word problem I need help figuring out please.?

Question

An automobile manufacturer can produce up to 300 cars per day. The profit made from the sale of these vehicles can be modeled by the function ... P(x)= -10x^2 + 1700x - 52,000

a) How many cars should be made and sold to maximize profit?

b) What is the maximum profit?

Answer 1

P´(x) = -20 x+1700 = 0 so x= 85 cars
P(85) =20,250 maximum profit