More formally, marginal revenue is equal to the change in total revenue over the change in quantity when the change in quantity is equal to one unit. This can also be represented as a derivative when the units of output are arbitrarily small. (Total revenue) = (Price that can be charged consistent with selling a given quantity) times (Quantity) or
), so marginal revenue is less than price. This means that the profit-maximizing quantity, for which marginal revenue is equal to marginal cost (MC) will be lower for a monopoly than for a competitive firm, while the profit-maximizing price will be higher. When demand is elastic, marginal revenue is positive, and when demand is inelastic, marginal revenue is negative. When the price elasticity of demand is equal to 1, marginal revenue is equal to zero.