Hey,

First of all, the basic eligibility for CAT is 50% in your graduation and you are in the safe harbor. Getting into an IIM is a different story though. Each IIMs have their own admission criteria and vary accordingly, and the weight given to CAT percentile is also different. Some colleges like IIM Bangalore depend heavily on your academics, which in your case could be of low chance ( IIM Bangalore expects 90-90-85 generally), but other IIMs like IIM-Calcutta go easy on the academics and weigh heavily on the CAT and this becomes your hunting ground. Thus, it becomes important for you to jot down the IIMs you are eligible for and aim for the particular CAT score accordingly. 

Your degree would give you an advantage though. Your arts degree fetches you additional marks while getting calls and also while converting the call during final admission. Again, the amount of weight given varies accordingly. But if you're an engineering grad, you might have a back foot.

Since nothing can be done about the academic score right now, it becomes rather important for you to score as high as possible in your CAT exam. Assuming you get somewhere around 98-99 percentile, there is a very high chance of you securing a seat given that you do your PI-WAT very well. With a score like 99+ percentile, you will certainly get calls from all the old IIMs, baby and new IIMs but please be assured that there is cutthroat competition by now. At around 96-97 percentile most of the new IIMs start giving calls and you stand a chance there because they go light on the academics. Getting a call from IIM B and IIM Indore is almost impossible with this academic record as they weigh heavily on it.

That being said, once you get a call from the IIMs, another obstacle to cross is the PI-WAT. Again, it depends upon different IIMs. Some IIMs like IIM Bangalore and IIM Indore give very less weight for your CAT percentile ( a mere 25%) and others like IIM Udaipur give 55% to your CAT score while calculating your composite score for the final admission. Thus scoring high only in CAT doesn't guarantee a seat and the real game begins only after that. Please prepare well and focus on current affairs and work experience related stuff if you get calls.

Find out about IIM admission criteria here - https://bschool.careers360.com/articles/iim-admission-criteria

Hope this helps.