g The average length of time it takes to complete a Ph. D. in statistics is 5.2 years, with a standard deviation of 0.7 years. In a random sample of 40 individuals with a Ph. D. in statistics, what is the approximate probability that the sample average of Ph. D. completion time was less than 5.4 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.