A solid disk of unknown radius R is initially at rotational rest. At t$=0$ s$,$ a constant force F$=40$ N is applied to the disk rim causing a counterclockwise torque of $55$ N$-$m $($see figure$)$ about its axis o$.$ Application of this torque causes the disk to increase its angular velocity $\backslash$omega at constant rate. If the disk's rotational kinetic energy at t $=5\mathrm{.}00$ s is $760$ J$,$ determine its angular acceleration $\backslash$alpha $($rad$/$s$2).$ Give answer to three places to the right of the decimal.