Long run equilibrium
In the long run, a monopolist can adjust his plant size or use the existing plant at any level so that he maximises his profits. The monopolist need not produce at the optimum level because of absence of competition. Therefore, he need not reach the minimum of LAC curve. On the other hand, he can stop at the point where his profits reaches maximum.
The monopolist will continue to make super normal profits in the long run as the entry of new firms is restricted.