X(z) is the z-transform of the signal x(n), then what is the z-transform of the signal nx(n)?

X(z) is the z-transform of the signal x(n), then what is the z-transfo

1.	X(z) is the z-transform of the signal x(n), then what is the z-transform of the signal nx(n)?
A.	(-z frac{dX(z)}{dz} )
B.	(z frac{dX(z)}{dz} )
C.	(-z^{-1} frac{dX(z)}{dz} )
D.	(z^{-1} frac{dX(z)}{dz} )
Answer» B. (z frac{dX(z)}{dz} )