It is claimed that Proactine, a medicine for acne, is 80% effective - that is, of every 100 persons who apply it, 80 show significant improvement. It is applied to the affected area of a group of 15 people. What is the probability that:

a) 10 will show significant improvement? Use the binomial probability formula to calculate your answer to six decimal places.

b) 13 or more people will show significant improvement? Use the binomial probability tables to calculate your answer.

c) Calculate the mean and standard deviation for this distribution. (Round the answers to one place after the decimal.)