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Which expression is equivalent to 2^4y^3

Lines a and b are perpendicular. if the slope of line a is 3, what is the slope of line b?

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.