Question: Answer the questions about the specified normal distribution.

a. The lifetime of ZZZ batteries are normally distributed with a mean of 280 hours and a standard deviation s of 10 hours. Find the number of hours that represent the 25^th percentile. (5 points)

b. Scores on an English placement test are normally distributed with a mean of 50 and standard deviation s of 2.5. Find the score that marks the top 10%. (5 points)