Tamika has $2.50 in quarters in her pocket, including 7 state quarters. She reaches into her pocket and takes out two quarters, one at a time. What is the probability that they are both state quarters?

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.