I was having an issue with this problem in my homework... was wondering if someone could help me out.

how many ways can u spell a 4 letter word using letters from CALCULATE using:

1) all different letters

2) two "a"s and another identical letter pair

3) two identical letter pairs

4) one pair of identical leters and 2 other different letters

and how many total 4 letter possibilities are there?

Thanks for your help!