There are 8 vacant chairs in a room. In how many ways can 5 persons take their seats?

How many numbers between 3000 and 4000 can be formed with the digits 1, 2, 3, 4, 5, 6?

There are 8 vacant chairs in a room. In how many ways can 5 persons take their seats?

How many numbers between 3000 and 4000 can be formed with the digits 1, 2, 3, 4, 5, 6?