Mathematics · Speed, Time and Distance

Three cars, P, Q, and R start from the same city to travel to the same destination in the same direction. Car P starts at 9:00 AM with a speed of 'x' km/h. Car Q starts at 9:30 AM with a speed of 'y' km/h. Car R starts at 10:00 AM with a speed of 'y + 10' km/h. Car Q overtakes car P at 10:30 AM. Car R overtakes car P at 11:00 AM. At what time will car R overtake car Q?