# Microeconomics question

I'm given this question. I'm not sure if I'm doing it right. Can any one help?

 Given the following short-run cost function: C=0.04q3 - 0.9q2 + 10q + 5

And the constant price of the final commodity of \$4 for the firm, determine:
a. The best level of output for the firm;
b. The level of profit the firm makes at this level of output;


a) Best level of output would be: MR which is 4, since price is 4, perfect competition, MC is the derivative of total cost, which is 0.12q^2-0.18q+10, then equating, 4=0.12q^2-0.18q+10, so q=0.75

b) putting q=0.75 and multiplying price by quantity, level of profit would be 4*0.75

• Verifying answers is not what we usually do here. Your post should include in detail the steps you took to arrive at your answers. Dec 13, 2020 at 18:05
• @AlecosPapadopoulos- I edited using my steps in details. I hope its fine now.
– user31619
Dec 13, 2020 at 19:01
• I’m voting to close this question because it is poorly formulated with no effort Dec 16, 2020 at 18:41

As for your second question: you confuse revenue with profit. Revenue is $$p*q$$, profit is $$p*q-c(q)$$