1. After New Year's many people join gym in order to get in shape. A specific gym that has kept track of visits notices that of those who join in January, 20% stop attending in February (never returns again). Let us say that this probability and condition is true for all gymnasiums.
a. If we chose three people at random, that joined the gym in January, determine the probability that all three stop attending in February?
b. Assume we choose four people at random who joined a gym in January. What is the probability that at least one person stops attending?
c. Assume we choose five people at random who joined a gym in January. What is the probability that exactly one person of the five stop attending?