Two cities X and Y are connected by a regular bus service with a bus leaving in either direction every T min. A girl is driving scooty with a speed…

Two cities X and Y are connected by a regular bus service with a bus leaving in either direction every T min. A girl is driving scooty with a speed of $\displaystyle 60$ km/h in the direction X to Y notices that a bus goes past her every $\displaystyle 30$ minutes in the direction of her motion, and every $\displaystyle 10$ minutes in the opposite direction. Choose the correct option for the period T of the bus service and the speed (assumed constant) of the buses.