is this the only photon energy that an electron in the n=6 energy level of a hydrogen atom could emit when it falls back to the n=2 energy level? explain

The uniform slender bar rests on a smooth horizon- tal surface when a force f is applied normal to the bar at point a. point a is observed to have an initial acceleration aa of 20 m/s2, and the bar has a corre- sponding angular acceleration of 18 rad /s2. deter- mine the distance b.