I am using C! to solve this issue
There are 6 N, 5 P and 4 D. In order to not select nickle twice in a row, we would only be selecting P and D -without replacement. Hence the formula should be
(5c1/9c1)X (4c1x8c1)
This gives me an answer of 5/18. What am I doing wrong? Plz advice.