I have attached a picture. The question is in the diagram itself.
The Attempt at a Solution
I tried to solve it by drawing free body diagrams and writing the equations but that seemed enormous and complex too and it seems that it will take a lot of time to solve it by that method. I know that this problem requires me to apply conservation of momentum and energy conservation principle but how? No doubt it can be solved by the traditional method but it would be too long and calculations will be extremely complex. There must be some easier way to do this.