please I need help with this,

24 card are put a pile in numerical order with 1 on the top and 24 on the bottom. they are first of all given a riffle shuffle so that the bottom card remains where it is, and then divided into four quarters. the bottom two quarters are left in the place they were in after the shuffle and the top two quarters are swapped over.

- work out the order of the cads after this combination of suffles has taken place.
- when this permutation is broken down into disjoint cycles,show that one of the cycles is (3 11 21 18 6 5) and find the other cycles.
- how many times will this process will have to be repeated to return all the cards to their original order? explain how you arrive at your answer.