When must a monopoly firm shut down?

"Monopoly is good for producers but bad for consumers. The gains of the former offset the losses of the latter. On balance,here is no reason to think that monopoly is bad for the economy." Is this statement true? Why or why not?

Is a monopolist subject to any competitive pressures? Explain. Would an unregulated monopolist have an incentive top operate and produce efficiently? Why or why not?

How will high entry barriers influence (a) the long-run profitability of firms, (b) the cost efficiency of firms in the industry, (c) the likelihood that some inefficient (high-cost) firms will survive, and (d) the incentive of entrepreneurs to develop substitutes for the products supplied by the firms? Are any competitive pressures present in markets with high barriers to entry? Discuss.

What are oligopolies? Why is oligopolistic collusion more difficult when there is product variation than when the products of all firms are identical?

What is price discrimination? Is it harmful to the economy? How does price discrimination affect the total amount of gains from exchange? Why do colleges often charge students different prices, based on their family income?