answer all questions with explanation

Problem 4 (Exponential Distribution). A small private ambulance service in Western Pennsylvania has determined that the time between emergency calls is exponentially distributed with a mean of 120 minutes. When a unit goes on call, it is busy for 50 minutes. If a unit is busy when an emergency call is received, the call is immediately routed to another service. The company is considering buying a second ambulance. However, before doing so, the owner would like to have answers to the following questions. (4.1) Easy What is the probability that an emergency call is received when the unit is busy? (4.2) Easy What is the probability that at least two hours elapse between an emergency call and the following one? (4.3) Easy The unit just went on call. What is the probability that the next emergency call will arrive between 50 minutes and two hours? (4.4) Moderate What is the distribution of the number of emergency calls received in 24 hours? What is the expected number of emergency calls received in 24 hours