Final answer:
Economists would expect Amy's demand for apples to increase if the price of sugar decreases because sugar and apples are complementary goods in baking.
Step-by-step explanation:
According to economic principles, when the price of a complementary good decreases, we would expect the demand for the related good to increase. In this scenario, since sugar is a complement to apples in baking, if the price of sugar decreases, we would expect Amy's demand for apples to increase. This can be explained by the fact that the lower cost of sugar makes it cheaper to bake items that use both sugar and apples, thus Amy would be more inclined to purchase more apples for her baking.