A wedge of mass $4\ \text{kg}$, with an inclined face at $30^\circ$ to the horizontal, rests on a smooth horizontal floor, as shown in the figure. A small block of mass $2\ \text{kg}$ is placed on the inclined face and released. All the surfaces are smooth, so the wedge is free to slide along the floor while the block slides down. Taking $g = 10\ \text{m/s}^2$, the acceleration of the wedge is closest to

Fig. 1: A wedge of mass 4 kg on a smooth floor, with its sloping face at 30 degrees, and a 2 kg block on the sloping face.