It's simple... you calculate your theorical BMR (Basal Metabolic Rate), let's say is 1800 (pretty common number)... now, of all the things you can do, you DON'T want to eat below your BMR (simply because it will eventually backfire...your body is clever), so your BMR is your "lower limit"...
once you know your BMR, you calculate your TDEE (total daily Energy expenditure) which is basically your BMR multiplied by an activity factor, say 55%, cause you train 5-6 days/week... to this number, now in the proximity of 3000 cals/day... you substract some 30% and you are good to go.
However, since you are planning on doing this for 4 weeks only, you could get away with eating at BMR (though thee risk of losing muscle elevates the lower you go with your caloric intake).
As for cardio, as much as you can, you want results fast? 5-6 times/week, 45 mins @ 75.80% of your heart capacity.
make sure you are hitting the weights HARD and HEAVY... you will not gain new muscle while on a caloric deficit, but you will help your body in keeping the muscle it already has