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Let C(x)C(x) and R(x)R(x) be the cost function and the revenue function for xx units of a commodity such that marginal cost of producing 2 units is equal to marginal revenue of selling 1 unit. If C(x)=ax3+bx2−12x+6C(x) = ax^3 + bx^2 - 12x + 6 and R(x)=100+6ax−bx2R(x) = 100 + 6ax - bx^2, then which one of the following is TRUE?

Solution

✅ Correct Option: 3

C′(x)=3ax2+2bx−12C'(x)=3ax^2+2bx-12 and R′(x)=6a−2bxR'(x)=6a-2bx.

Setting C′(2)=R′(1)C'(2)=R'(1): 12a+4b−12=6a−2b12a+4b-12=6a-2b.

This gives 6a+6b=126a+6b=12, i.e. a+b=2a+b=2, so a+b−2=0a+b-2=0.

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