There are several perspectives one can take on profit maximization. First, since profit equals
revenue minus
cost, one can plot
graphically each of the variables revenue and cost as functions of the level of output and find the output level that maximizes the difference (or this can be done with a table of values instead of a graph). Second, if specific
functional forms are known for revenue and cost in terms of output, one can use
calculus to maximize profit with respect to the output level. Third, since the
first order condition for the optimization equates
marginal revenue and
marginal cost, if marginal revenue (\text{MR}) and marginal cost (\text{MC}) functions in terms of output are directly available one can equate these, using either equations or a graph. Fourth, rather than a function giving the cost of producing each potential output level, the firm may have input cost functions giving the cost of acquiring any amount of each input, along with a
production function showing how much output results from using any combination of input quantities. In this case one can use calculus to maximize profit with respect to input usage levels, subject to the input cost functions and the production function. The first order condition for each input equates the
marginal revenue product of the input (the increment to revenue from selling the product caused by an increment to the amount of the input used) to the marginal cost of the input. For a firm in a
perfectly competitive market for its output, the revenue function will simply equal the market price times the quantity produced and sold, whereas for a
monopolist, which chooses its level of output simultaneously with its selling price. In the case of monopoly, the company will produce more products because it can still make normal profits. To get the most profit, you need to set higher prices and lower quantities than the competitive market. However, the revenue function takes into account the fact that higher levels of output require a lower price in order to be sold. An analogous feature holds for the input markets: in a perfectly competitive input market the firm's cost of the input is simply the amount purchased for use in production times the market-determined unit input cost, whereas a
monopsonist’s input price per unit is higher for higher amounts of the input purchased. The principal difference between short run and long run profit maximization is that in the long run the quantities of all inputs, including
physical capital, are choice variables, while in the short run the amount of capital is predetermined by past
investment decisions. In either case, there are inputs of
labor and
raw materials. ==Basic definitions==