I 13. The revenue function for a new product is, R(x) = -2x2 + 17x + 4 where R is the revenue in thousands of dollars and x is the number sold in thousands. The cost function is C(x) = 5x + 8. (6 marks) a) Determine the maximum revenue. b) Determine the corresponding profit function, in simplest form. c) How many items must be sold to maximize profit?