A uniform solid cylinder of mass \(M\) and radius \(R\) is mounted on a fixed, horizontal, frictionless axle through its center. A light, inextensible cord is wrapped around the outer rim of the cylinder and attached to a block of mass \(m\). The block is released from rest, causing the cylinder to rotate as the cord unwinds without slipping. Which of the following expressions gives the downward acceleration \(a\) of the block, and what are the limiting values of \(a\) and the cord tension \(T\) as \(M \to \infty\) and as \(M \to 0\)?