Marginal revenue is defined as the additional revenue that a firm receives from
selling an additional unit of output or the change in total revenue divided by the
change in output. It can be calculated in discrete terms if you have data on the total
revenue associated with different levels of output, as shown in the fourth line of
Table 3.2. If you have a mathematical total revenue function, the marginal revenue
function can be calculated by taking the derivative of the total revenue function
with respect to output. (Because calculus is not required in this text, we will
supply any marginal revenue functions that you need.)