How many 6 digit numbers can be made using digits 1, 2, 3, 4, 5, and 6 without repetition such that the hundred digit is greater than the ten digit, and the ten is greater than the one digit? How many 4 digit numbers can be formed by using 0, 1, 2, 3, 4, 5, 6, and 7? How many of them are between 4000 and 6000?