A company provides fertilization, insect control, and disease control services for a variety of trees, plants, and shrubs on a contract basis. For $50 per month, the company will visit the subscriber’s premises and apply appropriate mixtures. If the subscriber has any problems between the regularly scheduled application dates, the company’s personnel will promptly make additional service calls to correct the situation. Some subscribers elect to pay for an entire year because the company offers an annual price of $540 if paid in advance. For a subscriber who pays the annual fee in advance, the company should recognize the related revenue