Hi, I don't know how to solve these problems. Can someone help me?

- Of 10 candidates, the first 6 are being interviewed in the morning, and the last 4 in the afternoon. In how many ways can the interviewer arrange a schedule?
- How many seven-digit phone numbers can be formed if the first digit cannot be 0 and repetition of digits is not permitted? if repetition of digits is permitted?
- Using the letters of the word YOUNG, tell how many different 5-letter combinations are possible if: the first letter must be Y? the vowels and consonants alternate, beginning with a consonant (Y is a consonant here and Y does not have to be first)?