Here is my question, I'm very confused. I struggle with word problems. Could someone please point me in the right direction?

A store has 10 identical boxed stereos to store on 3 shelves. How many ways can the boxes be

stored on the shelves if:

(a) there are no restrictions on the number of stereos on each shelf?

(b) the top shelf must have exactly 2 stereos on it?

(c) each shelf must have at least 2 stereos on it?

(d) no shelf can have more than 5 stereos on it?

Greatly Appreciated.

hmm for question (a)

is 3x 10! correct?