28. Incorrect. The answer is
false, not true. dAVC/dQ = 3Q^{2}/3 - 6*2Q +
11 + 0 = Q^{2 }-12Q + 11(Use the Constant Function, Power, and
Sum-Difference Rules). Setting it equal to zero, Q^{2} - 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 d^{2}AVC/dQ^{2} = 2Q
- 12. At Q = 6.5d^{2}TC/dQ^{2} = 2*6.5 - 12= 1>0. Therefore,
ATC(Q) is minimum at the optimal level 6.5.