The total revenue in Rupees received from the sale of x units of a product is given by

R(x) = 13x² + 26x + 15.

Find the marginal revenue when x = 7.

Marginal revenue (MR) is the rate of change of total revenue with respect to the number of units sold.

Then,

So, when x = 7 then,

MR = 26(7) + 26 = 208

Therefore, the marginal revenue when x = 7 is Rs. 208.