Question 873681
26 Letters, 10 Numbers 
Choosing four alphanumeric characters with no repeats...How many are There?
N
0 {{{26C4)}}}
1 {{{(26C3)(10C1)}}}
2 {{{(26C2)(10C2)}}}
3 {{{(26C1)(10C3)}}}
4 {{{(26C0)(10C4)}}}
25 Letters, 9 Numbers 
0 {{{25C4)}}}
1 {{{(25C3)(9C1)}}}
2 {{{(25C2)(9C2)}}}
3 {{{(25C1)(9C3)}}}
4 {{{(25C0)(9C4)}}}