Each weekday Mr Harper goes to the local library to read the newspapers. The time he spends travelling is a normal variable with mean 15 minutes and standard deviation 2 minutes. The time he spends in the library is normally distributed with mean 25 minutes and standard deviation 4 minutes. Find the probability that, on a particular day, Mr Harper

(a) is away from the house for more than 45 minutes,

(b) spends more time travelling than in the library.