Question

 How does a single-price monopoly determine the price it will charge its customers? Why can a monopoly make a positive economic profit even in the long run?

Answer 1

The monopoly price and quantity are found where marginal revenue equals marginal cost (MR = MC). And MC<P, because monopoly power allows to be price maker without a risk to lose consumers. That's  why monopoly makes a positive economic profit even in the long run