Use the MR = MC method to

(a) maximize profit Tr, and

(b) check the second-order conditions, given

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TR 800Q 7Q2 8000-702 (a) MR TR'800 - 14Q Equating MRMC to maximize profits, TC 20 Q + 800 + 150 = - MCTC' = 6Q2-20+80 800-140602 - 20+80 Solving for Q by moving everything to the right, 602 +120-720 = 0 6(Q2+20 120) = 0 6(Q 10)(Q+12) = 0 Q = 10 Q=-12 critical values (b) TR" = -14 TC" = 120-2 Since = TRTC and the objective is to maximize , be sure to subtract TC" from TR" or you will reverse the second-order conditions and select the wrong critical value. " = TR" - TC" =-14 120+2=-12Q12 "(10)=-12(10) - 12=-132 <0 concave, relative maximum Compare these results with Problem 10.22 (b).