Probability and statistics questions.

Suppose 100 people have taken a Random Breath Test (RBT), and most people used the mobile (disposable) measuring device, which takes 1 minute to use. It was administered on the road by a policeman, while the person taking the test sat in the car. Another set of people were asked to go to another vehicle and use a van-based (more accurate but lengthy process) to measure their blood alcohol content (BAC).Of the 80 people taking the mobile RBT, 7 received a positive reading. Of the 20 people taking the van RBT, 10 received a positive reading.

(a) What is the probability of a positive reading, when people took the mobile RBT?

(b) What is the chance that a person took the van RBT, if we know that they got a positive reading?

(c) We are interested in whether the drinking patterns were generally the same for people taking mobile-based or van-based. What type of statistical distribution would we use?