Circular Motion

 A racing car travels on a track (without banking) $ABCDEFA$ (Figure). $ABC$ is a circular arc of radius $2R$. $CD$ and $FA$ are straight paths of length $R$ and $DEF$ is a circular arc of radius $R=100 m$. The coefficient of friction on the road is $\mu =0.1$. The maximum speed of the car is $50 {\text{ms}}^{-1}$. Find the minimum time for completing one round.