Answer and explanation:
Yes, the fact that a consumer is willing to replace four pounds of generic store-brand sugar for two pounds of a brand-name sugar reflects a diminishing marginal rate of substitution. This type of marginal rate of substitution (MRS) explains how a consumer is willing to acquire less quantity of one good to get one more additional unit of another good that is equally satisfying. In a graph, the diminishing MRS is calculated using an indifference curve.