Answer:
The correct answer is: -4 (minus four).
Step-by-step explanation:
To begin with, the concept of "Marginal Rate of Substitution" indicates how much of a good a consumer is willing to sacrifice to obtain a unit more of another good without changing the total satisfaction of the consumer. Therefore that this term is explained as the difference between one good and the other and that is why that the concept comprehends the slope of the indifference curve. That is why that if Cheryl's MRS of apples for banas is four then she is willing to sacrifice four apples for one banana and that indicates that the slope of the indiference curve is minus four (-4) because the result is always negative because it shows the sacrifice.