Al is a medical doctor who conducts his practice as a sole proprietor. During 2023 , he recelved cash of $687,600 for medical services. Of the amount collected, $42,000 was for services provided in 2022. At the end of 2023, Al had accounts receivable of $94,800, all for services rendered in 2023. In addition, at the end of the year, Al received $13,500 as an advance payment from a health maintenance organization (HMO) for services to be rendered in 2024. a. Compute Al's gross income for 2023 using the cash basis of accounting. b. Compute Al's gross income for 2023 using the accrual basis of accounting. c. Advise Al on which method of accounting he should use. Al should use the of accounting so that he will not have to pay income taxes on the