Angad, Caroline and Sarah share some sweets in the ratio 4:2:1. Angad gets 20 sweets. How many sweets are there altogether?

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.