During the first 20 miles you average 8 miles per hour. During the last 6.2 you increase your average speed by 2 miles per hour. How long will it take you to tune the last 6.2 miles of the marathon?

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.