StressFree provides house-sitting for people while they are away on vacation. Some of its customers pay immediately after the job is finished. Some customers ask that the business send them a bill. As of the end of the year, StressFree has collected $600 from cash-paying customers. StressFree's remaining customers owe the business $900. How much service revenue would StressFree have for the year under the a. cash basis? b. accrual basis