Without repeats, 4*3*2*1 = 24
If repeats are allowed, then 4*4*4*4 = 256
99999
10
15 of them.
5040 numbers can be made.
24 of them.
There are 60480 numbers.
99999
There are 4^6 = 4096 such numbers.
8.
125
10
13579
5040 numbers can be made.
15 of them.
there are 22
6, if you don't repeat any numbers.
24 of them.