points$)$

The overdrive unit shown in Fig. $7\mathrm{.}44$ is sometimes used following a standard automolive transmission to further reduce engine speed. The engine speed $($after the transmission$)$ corresponds to the speed of planet carrier $3,$ and the drive shaft speed corresponds to that of gear $5$ ; sun gear $2$ is her$$ stationary. Determine the percentage additional reduction in engine speed obtained when the overdrive is active.

Figure $7\mathrm{.}44$ Overdrive unit.