Q1a) Think of as one unit.
Then are objects that can be arranged in ways.
Now you do part b).
Q2) The difficulty with this question is find an adequate model.
I think that we can conceive this as putting n identical balls into n distinct cells.
There are ways to put n identical balls into n distinct cells.
If we choose one cell to be empty then we must choose one of the remaining to contain two balls.
That can be done in ways.
So we get