Can someone help me with these questions. (It’s a quiz btw)

Four airplanes carrying a total of 400 passengersarrive at the detroit airport. the airplanes carry, respectively,50, 80, 110, and 160 passengers. a) one of the 400 passengers is selected uniformly at random. let x denote the number of passengers that were on theairplane carrying the randomly selected passenger. find var(x)for x as given in the problemb) one of the 4 airplane drivers is also selected uniformly atrandom. let y denote the number of passengers on the chosen driver’s airplane. find var(y) for y as given in the problem

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

Triangle abc is a right triangle. find the measure of side b. round to the nearest hundredth. a) 6.13 cm b) 6.71 cm c) 9.53 cm d) 10.54 cm e) 12.45 cm