A party of students rented a motor boat, Bee, and shared the cost equally. If the number of students had been 5 less, they could have used a smaller boat costing only half as much as Bee and the expense to each would have been 50 cents less. If there had been 10 more students in the party, they would have required a larger boat costing 20 per cent more than Bee, but the expense to each would have been 30 cents less. How many students were there in the party?