B. To get two students who suffer from allergies, we need to get an allergy sufferer for the first student and an allergy sufferer for the second student. Following along the top branches of the tree, we see that the probability is:

P(two allergy sufferers) = P(1st student has allergies and 2nd student has allergies)

= P(1st student has allergies) * P(2nd student has allergies | 1st student has allergies)= (18/40)(17/39) = 0.196

There is about a 20% chance of selecting two students with allergies.

C. 0.296154 or approx. 29.6%D. 0.703846E. 0.804

B. About 16.6% C. = 0.642096D. About 4.42%E. About 19.84%