The total revenue in Rupees received from the sale of $x$ units of a product is given by $R(x) = 3x^2 + 36x + 5$. Find the marginal revenue, when $x = 5$, where by marginal revenue we mean the rate of change of total revenue with respect to the number of items sold at an instant.

₹66

The correct answer is Option (4) → ₹66 ##

Since marginal revenue is the rate of change of total revenue with respect to the number of units sold, we have

$\text{(MR)} = \frac{dR}{dx} = 6x + 36$

When $x = 5$,

$\text{MR} = 6(5) + 36 = 66$

Hence, the required marginal revenue is ₹66.