HW question

A student asked in micro today about question 10d from chapter 8. I didn't know in class, so here is my response.

When a regulator sets a price that is lower than the unregulated price, it often raises the MR. To see this, take a look at figure 11.7. When the regulator sets a price of P(r), it changes the MR for the monopolist. Remember, the monopolist MR is lower than the price becuase it must "hurt itself" in order to increase output by lowering the price on all the previously sold units. But when there is a price control, the monopolist can sell more output without affecting its MR. It can sell extra units at the price control without having to lower the price. This price can be higher than the MR without the price control and can actually raise the MR the monopolist receives.