Marginal is rate of change of cost, revenue or profit with the respect to the number of units.
This means differentiate the cost, revenue or profit.
Marginal Revenue, R'(x) The derivative of R(x).
Marginal Cost Function, C'(x) The derivative of C(x).
Marginal Profit Function, P'(x) The derivative of P(x).
In words, the word “Marginal” can be read as “the next unit”,
Marginal Revenue, R'(x) The next unit will make this Revenue
Marginal Cost Function, C'(x) The next unit will be this Cost
Marginal Profit Function, P'(x) The next unit will make this Profit
