A four or five-digit PIN is to be selected from theeightdigits0,1,2,3,4,5,6,7.

1. How many5-digitPINs are possible if:
2. a) all 5 digits are the same?e.g. 7-7-7-7-7
3. b) no digit can be repeated?
4. c) any digit can be repeated?
5. d) the first 3 digits must be different digits and the last 2 digits must be the same, but none of the first 3 digits can be used in the last 2?
8. Supposeany digit can be repeated, how many5-digitPINs are possible if each PIN:
9. a) must end with "5"?
10. b) must not start with "3"?
11. c) must neither start with "7" nor end with "7"?

1. Supposeno digit can be repeated, how many4-digitPINs are possible if each PIN:
2. a) must end with "5"?
3. b) must not start with "3"?
4. c) must neither start with "7" nor end with "7"?