Exercise 2. A service facility charges a $20 fixed fee plus $25 per hour of service up to 6 hours, and no
additional fee is charged for service exceeding 6 hours. Suppose that the service time $\tau$ is equally
likely to be any number of hours in {1,2,3,4,..., 10} hours (Assume that it takes some integer
number of hours). Let X represent the cost of service in the facility.
(a) Find and sketch the probability mass function for X.
(b) Find and sketch the cumulative distribution function for X.
(c) What is the probability that you end up paying less than or equal to $70 for service? Answer this
part two different ways:
• Using your answer to part (b).
• Finding the time (call it $\tau_0$) at which the service would cost exactly $70 and then finding the
probability that $\tau \le \tau_0$.
(d) What is the expected value (or mean) of X?
(e) The repair shop calls after 4.5 hours and tells you that your car is not ready yet; hence, this is going
to cost you at least $145. Given this information, come up with a new probability mass function for
how much it will cost.
```