The money to be spent for the welfare of the employees of a firm is proportional to the rate of change of its total revenue (marginal revenue). If the total revenue (in rupees) received from the sales of x units of a product is given by R(x) = 3x² + 36x + 5, find the marginal revenue when x = 5, and write which value does the question indicate.

If the Total Revenue is given by f(x), the Marginal Revenue is the rate of change of total revenue and is nothing but the first order derivative of the function df(x)/dx
Total revenue = R(x) = 3x² + 36x + 5
Differentiating the equation R(x), we get
dR(x)/dx = 6x + 36
If x = 5, Marginal revenue = 6(5) + 36 = 66.
Therefore, the Marginal revenue = 66.
The concern over the welfare of the employees by the employer.