Indirect Mail Inc. had been mailing out coupons for a clearance sale at a constant rate for 4 days, when they counted the coupons, they still had mail out and discovered they had 120,000 left. After 7 total days of work they had 75,000 left. At what rate

Indirect Mail Inc. had been mailing out coupons for a clearance sale at a constant rate for 4 days, when they counted the coupons, they still had mail out and discovered they had 120,000 left. After 7 total days of work they had 75,000 left. At what rate are they mailing coupons out?