Answer: a) increase in the demand for Kindles.
Explanation: the substitution effect for substitute goods gives that, if the price of good A rises, the demand for good B rises. Since a substitute good is a good that can be used in place of another, they are goods that a consumer perceives as similar or are comparable, in such a way that having more of one good causes the consumer to desire less of the other good. From the viewpoint of price, and given that consumers always prefer to spend less in instances where two goods are substitutes, it then means that Kindle can be used and preferred in place of Nooks given that the price of Nooks had gone up. Therefore, increasing the price of Nooks causes a corresponding increase in the demand for Kindles.
