12. The total cost function at a certain company is TC = 100 + 4Q + 8Q', where TC is total costs and Q is the output. a. What is the marginal cost when output is 10? (1 p.) b. What is the marginal cost when output is 12? (a pt.) c. What is the marginal cost when output is 20? (1 92) Find the partial derivative of Y with respect to X in cach of the following cases: a. Y= 10 + 3Z + 2X a p) 13. b. Y=18Z +4x' a n) c. Y-3+ 10X + 5X (1 p.)