can a monopolist can sell any quantity he likes at a price ???/
Monopolist can not sell any quantity at a price fixed by him. He has no control over the quantity that he can sell in the market, as it depends on the buyers that what quantity of output they want to purchase at the price fixed by the monopolist. If the monopolist fixes a higher price, then lesser quantity of the output will be demanded and lesser quantity will be sold in the market. On the other hand, if he fixes a lower price, then higher quantity of the good will be sold. This implies the negative relationship between the monopolist's price and the quantity demand by the buyers.