Pedro drives the same route to work on Monday through Friday. His route includes one traffic light. According to the local traffic department, there is a 55% chance that the light will be red on a randomly selected work day. Suppose we choose 10 of Pedro’s work days at random and let Y = the number of times that the light is red.

a. Explain why Y is a binomial random variable.

b. Find the probability that the light is red on exactly 7 days.