In the following arrangement, the system is initially held at rest by an external agent. At $t=0$, the $5 \mathrm{kg}$ block is released. If the acceleration of block $\mathrm{C}$ is $\frac{x}{10} \mathrm{m}{\mathrm{s}}^{-2}$, then find the value of $x$. Assume that the pulleys and strings are massless and smooth. [$g=9.8\mathrm{ }\mathrm{m}{\mathrm{s}}^{-2}$]