For Matthew, the marginal utility of the 9th soda in a day is positive and the marginal utility of the 10th soda in a day is zero. This
◦ implies that Matthew's demand curve for sodas per day will become upward sloping at 10 sodas per day.
◦ is impossible because each additional unit of consumption of any good must provide positive marginal utility.
◦ implies that at a zero price Matthew's demand curve will intersect the quantity axis at 10.
◦ implies that Matthew maximizes utility by consuming 9 sodas per day.