(31) Al is a medical doctor who conducts his practice as a proprietor. During 2013, he received cash of $280,000 for medical services. Of the amount collected, $40,000 was for services rendered in 2012. At the end of 2013, Al had accounts receivable of $60,000, all for services rendered in 2013. In addition, at the end of the year, Al received $12,000 as an advance payment from a health maintenance organization (HMO) for services to be rendered in 2014. Compute Als gross income for 2013: a. Using the cash basis of accounting. b. Using the accrual basis of accounting. c. Advise Al on which method of accounting should be used