The ques is below....u have 2 show the work!!! i need this ASAP!!!?

a manufacturer finds that it costs him x^2+5x+7 dollars to produce x tons of an item.At production levels above 3.he must hire additional workers,and his cost increase by 3(x-3) dollars on his total production.If the price he receivs is $13 per ton regardless of how much he manufactures and if he has a plant capacity of 10 tons, what level of output maximizes the profits?