Question:
The total revenue in Rupees received from the sale of x units of a product is given by
$R(x)=3 x^{2}+36 x+5$. The marginal revenue, when $x=15$ is
(A) 116 (B) 96 (C) 90 (D) 126
Solution:
Marginal revenue is the rate of change of total revenue with respect to the number of units sold.
$\therefore$ Marginal Revenue $(\mathrm{MR})=\frac{d R}{d x}=3(2 x)+36=6 x+36$
$\therefore$ When $x=15$
$M R=6(15)+36=90+36=126$
Hence, the required marginal revenue is Rs 126.
The correct answer is D.