28. Incorrect. The answer is false, not true. dAVC/dQ = 3Q2/3 - 6*2Q + 11 + 0 = Q2 -12Q + 11(Use the Constant Function, Power, and Sum-Difference Rules). Setting it equal to zero, Q2 - 12Q + 11 = 0, we obtain the roots of the quadratic equation Q = 6.5 and Q = -18.5. The latter makes no economic sense, therefore, the candidate for the optimal level of production is Q=6.5. Checking second order conditions d2AVC/dQ2 = 2Q - 12. At Q = 6.5d2TC/dQ2 = 2*6.5 - 12= 1>0. Therefore, ATC(Q) is minimum at the optimal level 6.5.