CA Foundation · Quantitative Aptitude · Differential and Integral Calculus
The total revenue function of a firm is R(x) = 60x − 0.5x² (in ₹). The output at which marginal revenue becomes zero is:
Marginal revenue is the derivative of revenue, which is 60 − x here. Setting it to zero gives an output of 60 units, and since the second derivative is negative, total revenue is maximised at this output.
- A30 units
- B60 unitsCorrect
- C120 units
- D90 units
Explanation
MR = dR/dx = 60 − x. Setting MR = 0 gives x = 60. Check: R''= −1 < 0, so revenue is maximum there. The value 120 comes from wrongly solving 60 − 0.5x = 0, and 30 from halving 60.
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