Sofia is taking three exams at the end of this semester, one in each of the following courses: Mathematics, Statistics, and Economics. She estimates that the probability of passing the Mathematics exam is 0.85, the Statistics exam 0.75, and the Economics exam 0.90. If the three events “Success in subject i” are completely independent, where i takes the values “Mathematics,” “Statistics,” and

“Economics,” find the probability function of X, denoting the number of passes in her exams.