The distance d of a particle moving in a straight line is given by d(t) = 27° + 5t - 2, where t is given in seconds and dis measured in meters.

Find an expression for the instantaneous velocity v(t) of the particle at any given point in time.

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.