Four buses carrying 153 high school students arrive to montreal. the buses carry, respectively, 38, 44, 25, and 46 students. one of the studetns is randomly selected. let x denote the number of students that were on the bus carrying this randomly selected student. one of the 4 bus drivers is also randomly selected. let y denote the number of students on his bus. compute the expectations and variances of x and y.