QUESTION $4.$ A $20$ kg mass is hung on the end of the cable wrapped around the core of cylinder A$,$ whose mass moment of inertia is $10$kg $*$ m$^2,$ as shown in the figure. After the cable wrapped around the outside of cylinder A passes through pulley B$,$ which has a mass moment of inertia of $3$kg $*$ m$^2,$ an $80$ kg mass is hung on its end. At this moment the system is stationary. At t $=0,$ the block with a mass of $80$ kg is released to move downwards. Calculate the angular acceleration of cylinder A and the acceleration of the $20$ kg block at the given instant. $($Note: T$1,$ T$2,$ T$3$ are the tension forces in the cables. Assume that there is no slippage between the cables and the rollers$)$ g $=9\mathrm{.}8$m $/($s$^2)($ find the acceleration$)$