A monopolist makes water-powered hover boards. At a price of $750 each, the monopolist can sell 13 hover boards. At a price of $725 each, it can sell 14 hover boards. Assume the monopolist cannot price discriminate. When charging $750 per hover board, total revenue is [ Select ] . When charging $725 per hover board, total revenue is [ Select ] . This means that the marginal revenue of selling the 14th hover board is [ Select ]