Answer:
The answer is: C) Increase his consumption of product Y and decrease his consumption of product X.
Explanation:
The equi-marginal utility principle states that a consumer will spend his money buying different goods that provide him or her the maximum possible satisfaction.
In Oscar's case, each extra unit of product X delivers 10 units of satisfaction, but product X costs $5. Instead he should buy product Y, which costs $1, and gives him 8 units of satisfaction. By consuming product Y, Oscar is getting 8 units of satisfaction per dollar spent, while he only gets 2 unit of satisfaction per dollar spent with product X.