Need help on this, keep getting the wrong answer according to back of the book. Assignment is not due just reg hw. If done right ill give you a super rating

12. The demand for a t-shirt is 25,000 t-shirts when the price is $10 each, and 10,000 when the price is $13 each. If the cost to produce one t-shirt is $8 each and fixed costs are $5000. (6 marks) a. Find the cost, revenue and profit functions. b. Find the marginal profit when q = 20,000. And interpret the marginal profit. c. Find where the marginal profit is $3000/t-shirts