Diminishing marginal returns differs from diminishing returns. The effective rate is usually lower than the marginal rate. The falling MP is due to the law of diminishing marginal returns. The same law emerges in the law of diminishing marginal returns. This is known as the law of diminishing marginal rate of substitution. Menger also developed the law of diminishing marginal utility. Demand is inelastic at every quantity where marginal revenue is negative. A company maximizes profit by selling where marginal revenue equals marginal cost. The inverse demand function is useful in deriving the total and marginal revenue functions. Demand is unit elastic at the quantity where marginal revenue is zero. Markup is the difference between price and marginal cost. Copulas are important because they represent a dependence structure without using marginal distributions. Yet this land was of marginal agricultural value. It branches into the posterior descending artery and the right marginal artery. Thus, entrepreneurship brings prices closer to marginal costs.