How to solve question b and c ?

Four people will enter an automobile showroom, and each will either purchase a car (P) or not purchase a car (M). a. Draw a tree diagram depicting the sample space of all possible purchase decisions that could potentially be made by the four people. b. List the sample space outcomes that correspond to each of the following events: 1. Exactly three people will purchase a car. 2. Two or fewer people will purchase a car. 3. One or more people will purchase a car. 4. All four people will make the same purchase decision. c. Assuming that all sample space outcomes are equally likely, find the probability of each of the events given in part b