In Exercise 29, results were reported from a study evaluating the effectiveness of LASIK eye surgery. The study found that 10% of eyes that underwent LASIK surgery needed to be retreated. If the Edmonds Eye Clinic performs the operation on 50 eyes this week, what is the probability (using the Poisson approximation) that
a. Exactly seven eyes will need re-treatment?
b. No more than two eyes will need retreatment?
c. At least four eyes will need re-retreatment?