Think about it like this...

1. the rod moves to the right. The area abcd increases.Thus the flux through abcd increases
2. abcd will try to oppose this change - thus, the direction of the induced current has to be in such a way so that the magnetic field created by abcd is out of the page (you can think of the field lines that are coming out of the page as cancelling some of the magnetic field lines going in to the page)

 3.to do this, an anticlockwise current is required, this means current flows from b to a