I had quit my job in July in order to prepare for CAT. Is that going to be a problem to explain in the interview? 

It will be a good idea to spend the time working in an NGO or joining a start up of family business. It will be a bad idea to tell professors that you quit your job to prepare for CAT. It would mean that students who worked while preparing for CAT are better at managing their time. 

So, it doesn't matter that you quit your job, just try to explain how you spent this time in a productive manner. 

All the best