$($III$)$ Consider the same situation as in $($II$)$ except that the block on the left is moving down its incline, while the block on the right is moving up along its incline. Two blocks, one with mass $M$ and the other $2M,$ lie on separate frictional inclined planes, one at $16\mathrm{.}260$ and the other at $73\mathrm{.}740.$ The coefficient of kinetic friction acting between the block on the left is ${}_{k,1}=\frac{1}{8}$ and that on the right is ${}_{k,r}=\frac{4}{7}.$ The blocks are joined by ideal rope which passes over an ideal pulley. The system is in motion, with the block on the left moving down along its incline while the one on the right is moving upward.

$($a$)$ Draw FBDs for each of the blocks.

$($b$)$ Determine the acceleration of the system of blocks in this case.

$T=2ma-F_k$