Stephen runs a pet salon. he is currently grooming 120 dogs per week. if instead of grooming 120 ​dogs, he grooms 121 dogs, he will add ​$68.24 to his costs and ​$66.78 to his revenues. what will be the effect on his profits of grooming 121 dogs instead of 120 ​dogs? ​stephen's profits will change by ​$ nothing. ​(enter your response rounded to two decimal​ places.)