Joe's utility function for movies at the theater (T) and DVDs watched at home (D) is given by U = 4 T² + D²

1. Calculate the marginal utilities for each good.
2. Write an equation for MRS_TD.
3. Would bundles of (T = 2 and D = 2) and (T = 1 and D = 4) be on the same indifference curve?
4. Are Joe's indifference curves convex? (Does MRS_TD fall as T rises?)