Walter found out that after working for 9 months he had earned 6 days of vacation time. how many days will he have earned after working for 2 years?

The coverage of a base station of a telecommunication company forms a disk with a radius of (kilometers). let be the distance of a cellphone from a base station. assume that the location of cellphones in use are randomly uniformly distributed within the disk. calculate the mean and variance for the random variable.