So, permutation is when the order does matter
The combination is when it doesn't.
[tex]P=\frac{n!}{(r\text{ - }n)!}=\frac{4!}{2!}=\frac{4(3)(2!)}{2!}=4\text{ x }3=\text{ }12[/tex]That would be a, then: Combination
[tex]C=\frac{n!}{r!(n\text{ - }r)!}=\frac{4!}{2!(2!)}=\frac{4(3)(2!)}{2!(2!)}=\frac{4(3)}{(2)(1)}=\frac{12}{2}=6[/tex]So, a is 12 and b is 6