The demand for a certain product is represented by the function $p=200+20 x-x^2$ where x is the number of units demanded and p is the price. Then the value of marginal revenue when 10 units are sold is:

300

The correct answer is Option (2) → 300

$p = 200 + 20x - x^2$

$\text{Revenue } R = x \cdot p = x(200 + 20x - x^2)$

$= 200x + 20x^2 - x^3$

$\text{Marginal Revenue } = \frac{dR}{dx} = 200 + 40x - 3x^2$

$MR(10) = 200 + 400 - 300 = 300$

$\text{Marginal Revenue at } x=10 \text{ is } 300$