Rashid's indifference curves "do" display diminishing marginal rate of substitution because "the magnitude of the slope of both indifference curves decreases as Rashid consumes more albums and fewer books".
The Law of Diminishing Marginal Rates of Substitution expresses that MRS diminishes as one moves down the standard convex-shaped curve, which is the lack of concern bend. For instance, a shopper picks amongst cheeseburgers and hotdogs.