Average talk time between charges of a cell phone is advertised as 4 hours. Assume that talk time is normally distributed with a standard deviation of 0.8 hour.
a. Find the probability that talk time between charges for a randomly selected cell phone is below 3.5 hours.
b. Find the probability that talk time between charges for a randomly selected cell phone is either more than 4.5 hours or below 3.5 hours.
c. Twenty five percent of the time, talk time between charges is below the 1st quartile value. What is this value?