Read the description of f below, and then use the drop-down menus to complete an explanation of why f is or is not a function. f relates each student in Mr. Well's history class to their score on a final exam.

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.