Under american institute of certified public accountants rules, which statement best describes the period of the professional engagement as it applies to a three-year engagement to audit a client's financial statements? a.) it begins each year when fieldwork commences and ceases when fieldwork ends. b.) it begins when the engagement letter is signed and ceases each year when the report is issued. c.) it begins when fieldwork commences and ceases when the report is issued, recommencing when fieldwork begins again for the next period. d.) it begins when the engagement letter is signed and continues until the report for the third year is issued unless the relationship is terminated sooner.