Let x_n=n*(1/2)^n*u_n. Find the z-transform of x_n. A n/[1-(2z)^(-1)] B (2z)^(-1)/[1-(2z)^(-1)] C -(2z)^(-1)/[1-(2z)^(-1)]^2 D (2z)^(-1)/[1-(2z)^(-1)1^2If the z-transform function is X(z)=2/(2-z^{-1}), find the corresponding sequence. A un B (0.5)^n*u_n C 2*(0.5)^n*u_n D 2^nu_n