As a receptionist of a veterinarian, one of Michelle Johnson's tasks is to schedule appointments. She allows 20 minutes for a routine visit and 40 minutes for surgery. The veterinarian cannot do more than 6 surgeries per day. The office has 7 hours available for appointments. If an office visit costs $55 and most surgeries costs $125, find the combination of office visits and surgeries that will maximize the income the veterinarian practice receives per day.