The marginal revenue MR =800-6q and the average cost function AC=5+300/q.Find the profit when 10 units are produced and sold

If variable costs for a firm is $660, the average total cost is $8, and the firm sells 120 units, what are the firm's fixed costs?

Whenever the Total revenue is $31 and the explicit costs is $20 find the Accounting profit.

As a producer and seller of some commodity, you have learned that, if you produce and sell x itmes in a particular month, the following functions can be used to find the cost and revenue: Revenue: R(x)=150x-x^​2 and Cost: C(x)=3000+20x.  (a) Write a simplified formula for your profit in a particular month, P(x)=R(x)- C(x) (b) Find the "break-even" point(s) (c) How many items should you produce and sell in a month in order to achieve a maximum profit? (d) What is the maximum possible monthly profit? This is the problem and I cannot solve the c and d, could you please help me?