Four buses carrying 157157 high school students arrive to montreal. the buses carry, respectively, 3636, 4545, 3030, and 4646 students. one of the studetns is randomly selected. let xx denote the number of students that were on the bus carrying this randomly selected student. one of the 44 bus drivers is also randomly selected. let yy denote the number of students on his bus. compute the expectations and variances of xx and yy:

At wind speeds above 1000 centimeters per second (cm/sec), significant sand-moving events begin to occur. wind speeds below 1000 cm/sec deposit sand and wind speeds above 1000 cm/sec move sand to new locations. the cyclic nature of wind and moving sand determines the shape and location of large dunes. at a test site, the prevailing direction of the wind did not change noticeably. however, the velocity did change. fifty-nine wind speed readings gave an average velocity of x = 1075 cm/sec. based on long-term experience, σ can be assumed to be 245 cm/sec. (a) find a 95% confidence interval for the population mean wind speed at this site. (round your answers to the nearest whole number.) lower limit cm/sec upper limit cm/sec