A doll making small-scale unit calculates the variable cost of making \(x\) number of dolls per day as three times the square of \(x\). The fixed cost of packaging \(x\) dolls is Rs. 2800. The marginal cost of producing 120 dolls :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Rs. 720
Total cost = variable cost + fixed cost:
\(C(x) = 3x^2 + 2800\)
The marginal cost is the derivative of the total cost. The fixed cost is a constant, so it adds nothing to it:
\( \displaystyle MC = \frac{dC}{dx} = 6x \)
At x = 120:
\(MC = 6 \times 120 = 720\)
So the marginal cost is Rs. 720.
CBSE Applied Mathematics (Class XII):
Marginal Cost and Marginal Revenue
