Momentum + Pendelum Question

Hi, I need help with a question on a practice exam. I got the first two questions, but I have no clue on where to start as to figuring out how far the cart has moved. Anyone have any suggestions? Thanks!

A cart of mass M = 9 kg rolls without friction on a horizontal surface. It is attached through a freely pivoting initially-horizontal massless rod of length L to a ball of mass m = 3 kg. The system is initially at rest when the ball is released. The pendulum swings down and to the left, and at the bottom of its swing the ball is observed to have a velocity of 3.5 m/sec to the left.

http://online.physics.uiuc.edu/cgi/c.../fa10/fig3.gif

What is the speed of the cart when the ball is at the bottom? 1.17 m/s

What is the length L of the pendulum? 83 m

How far to the right has the cart moved, when the ball is at the bottom??

Comment on jcaron2's post

The answer according to the practice test is L/4 or 1/4 of the length of the pendulum. I see how L/3 is possible but how does L/4 work?