A recent census at a major university revealed that 60% of its students mainly used Macs. The rest mainly used PCs. At the time of the census, 67% of the school’s students were undergraduates. The rest were graduate students. In the census, 23% of respondents were graduate students and used a Mac as their main computer. Suppose we select a student at random from among those who were part of the census. Define events G: is a graduate student and M: primarily uses a Mac.

a. Find P(G ∪ M). Interpret this value in context.

b. Consider the event that the randomly selected student is an undergraduate student and primarily uses a PC. Write this event in symbolic form and find its probability.