Suppose Paul's preferences for X and Y (the only two goods available for consumption) are described by the "atypical" utility function U=X+2Y. Which of the following statements correctly characterizes this utility function? a) The function exhibits diminishing marginal utility of X. b) The function exhibits increasing marginal utility of X. c) The marginal utility of X is always negative. d) Paul regards X as a "bad" good, meaning its consumption leads to a decrease in utility. e) None of the above