The problem I am working is the following; please provide step-by-step to obtain solution's.
I am unable to figure (c) out the ANSWER IS ... 7805
There are 5 rotten plums in a crate of 25 plums, How many samples of 4 of the 25 plums contain at least one rotten plum?
However you seem to be on the right track (looking at your correct answers to a and b), so try to solve it this way.
the number of possibilities to pick AT ...
The solution explains how to calculate the probabilities of several events.