A wooden block (block W) and a metallic block (block M) are tied together by a lightweight cord and slide down an inclined plane at an angle $\theta ={30}^{\circ }$ to the horizontal. The masses of the blocks are $m_W=m_M=5.0kg$. The coefficients of friction for the wooden and metallic blocks are ${\mu }_W=0.25$ and ${\mu }_M=0.35$, respectively. Calculate the acceleration of the system as the blocks slide down the incline.