A coin dealer is having paper wraps made to go around a
stack of coins. The coins have a diameter of 12 mm, and
the dealer states that the paper should be exactly 36 mm
wide, or 3 times the diameter, to go around the coins. Is
the coin dealer correct? Explain.

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.