Diminishing, Increasing and Constant Marginal Utility

For each of the following situations, decide whether Al has increasing, constant, or diminishing marginal utility.

a. The more economics classes Al takes, the more he enjoys the subject. And the more classes he takes, the easier each one gets, making him enjoy each additional class even more than the one before.

b. Al likes loud music. In fact, according to him, "the louder, the better." Each time he turns the volume up a notch, he adds 5 utils to his total utility. --- this one is Constant

c. Al enjoys watching old episodes of the sitcom Friends. He claims that old episodes are always funny, but he does admit that the more he sees an episode, the less funny it gets.