helpppp .. the text book I'm using explains what are combinations and permutations but doesn't say anything about repeated letters.

(always hated probability) :x

Problem:

**Find the number of (a) combinations and (b) permutations of **__four__ letters each that can be made from the letters of the word *Tennessee*.
Please show me how to come up with the answer.

It says the answer key is (a) 17, (b) 163.

I have no freakin clue how to get both answers.