Finding Maximum Profit from Cost f(x)

Greetings.

C(q)= .25q^2+8q+25
p(q)= 83-q

I need help finding the maximum profit, and with what q value.

For the profit function I have P(q)=-1.25q^2-75q-25

To maximize profit I got -30. This is clearly wrong so any direction would be of great value.

Thanks.

For what do C, q, p, and P stand?

Thank you! (Itwasntme)

C = Cost
p = Price
P = Profit
q = Quantity

Sorry.