Choose the correct answer in the total revenue in Rupees received from the sale of $x$ units of a product is given by $Rx = 3x^2 +36x + 5$. The marginal revenue, when $x = 15$ is

Question

$(A)\; 116 \qquad (B)\; 96 \qquad (C)\; 90 \qquad (D)\; 126$