Two trains A and B are entering a railway platform from opposite direction. The length of the platform is 300 m. The speed of B is two times the speed of A. The time taken by B to cross the platform is one-third of the time taken by A to cross the platform. If the sum of the lengths of A and B is 500 m, what is the difference in their lengths? **[CAPF (ACs) 2025]**