The termination of a chemical reaction occurs at a random time between 4.5 and 6 hours after the start of the experiment. The termination time follows a uniform distribution.
a. What is the probability that the reaction lasts at least 4.75 hours and no longer than 5.2 hours?
b. Given that the reaction hasn't terminated by the five-hour mark, what is the probability that it will terminate within 20 additional minutes?