Let [math]X[/math] be a random variable with density function [math]f_X[/math], and let [math]Y = X + b[/math], [math]Z = aX[/math], and [math]W = aX + b[/math], where [math]a \ne 0[/math]. Find the density functions [math]f_Y[/math], [math]f_Z[/math], and [math]f_W[/math]. (See Exercise.)