Revenue (R) = (Number of units sold)*(price per unit)
R = x*p(x) = -(1/5)x2 + (95/3)x
Profit (P) = Revenue - Cost
P = -(1/5)x2 + (95/3)x - (2/5)x2 - 9x - 33
P = -(3/5)x2 + (48/5)x - 33
To find the production (x) that maximizes profit, take the derivative of P wrt x, set it to zero, and solve for x.