The distribution of battery life of MacBook laptops is normally distributed with a mean of 8.1 hours and a standard deviation of 1.3 hours. The distribution of Dell laptops is normally distributed with a mean of 6.8 hours with a standard deviation of 0.9 hours.

a. Calculate the probability that a randomly selected MacBook laptop battery lasts more than 9 hours.

b. Calculate the probability that a randomly selected Dell laptop battery lasts between 6 and 8 hours.

c. How long must a MacBook laptop battery last to be in the top 3%?

d. How long must a Dell laptop battery last to be at the 30th percentile?

e. Calculate the probability that a randomly selected MacBook laptop lasts longer than the 25th percentile of Dell laptops.

f. Calculate the probability of a MacBook lasting more than 8.5 hours and calculate the probability of a Dell lasting more than 8.5 hours.