If the Marginal Utility of the 3ʳᵈ Cup of Coffee

Multiple Choice

If the marginal utility of the 3ʳᵈ cup of coffee is 23 and the marginal utility of the 4ᵗʰ cup is 15, then:

A) it is optimal for the consumer to have 3 cups of coffee.
B) the price of a cup of coffee must be relatively low.
C) it is optimal for the consumer to have 4 cups of coffee.
D) there is evidence of diminishing marginal utility.