There are 4 letters. Using some simple math, we find that 4! = 4*3*2*1 = 24.
There are 24 combinations.
You can test this with smaller numbers to see if it works. For example. PIG
3! = 3*2*1 = 6
PIG PGI GIP GPI IGP IPG
There are 24 combinations.
You can test this with smaller numbers to see if it works. For example. PIG
3! = 3*2*1 = 6
PIG PGI GIP GPI IGP IPG