Hi, I'm unable to solve this question

7-In a bookshop, the weights of books are modelled by a normal distribution with mean 8.5kg and standard deviation 1.5 kg

(a) Determine the probability that a randomly selected book will weigh between 8 kg and 9 kg

(b) A hardcover will be given by the store as a gift to its customer. The cover has a normal distribution with mean 3.5 kg and standard deviation 0.4 kg. What is the probability that a randomly selected hard covered book will weigh more than 7.6 kg?

(c) Determine to two decimal places the weight exceeded by 30% of the hard covered books.

(d) 50 books were selected from the uncovered books, what is the probability that more than half will weigh less than 9 kg?