Can you show a breakdown of how you solve this problem

A study finds that the distribution of driving speeds of commercial trucks on interstate highways in California is normal with mean 70 mph and standard deviation 5.0.

a)What is the probability that a randomly selected truck is going over 72 mph?

b)Given that a randomly selected truck is going over the speed limit of 65 mph, what is the probability that this truck is going over 75 mph?

c)If the Highway Patrol randomly chooses 10 trucks to monitor, what is the probability that the average speed of the sample of 10 trucks will be over the speed limit of 65 mph?

d)A second sample of 20 trucks is to be obtained. What is the probability that the average speed obtained in the second sample will differ from the average speed obtained in the first sample by more than 5 mph? You may assume that both samples are random and independent.