I need help on this question from 'Using the Consumer Behavior Model' chapter.

I 3. Suppose that Karen's utility function is given by U = 2A + SE. a. Calculate Karen's marginal utility of good A and her marginal utility of good B. (2 points) b. Suppose that the prices of the goods PA and PB are such that Karen is (optimally) consuming positive quantities of both goods. What is the price of good A in terms of the price of good B? (2 points) c. How will her consumption change if PA doubles, while PB does not change? (2 points)