Hi all. This question is in a chapter that involves permutations and combinations and I'm a little thrown by it. I can't work out the answer to c)

i have the following for:

a) 0.50

b) 0.25

c)????

I think c) is just 0.25 as well...but have a feeling I'm wrong...or could have a/b. wrong as well! please help! there are no answers in the back of the book.

many thanks!