(a) Every person, subject to the payment of the tax hereby imposed who has commenced his business at least one (1) full year prior to the beginning of any license year shall compute his annual gross volume of business upon the actual gross amount of business transacted by him during the preceding calendar year.

(b) Every person, subject to the payment of the tax hereby imposed, who has commenced his business less than one (1) full year prior to the license year one thousand nine hundred forty-eight, for the license year one thousand nine hundred forty-eight, or who has commenced his business subsequent to the beginning of any license year for such license year and the succeeding license year, shall compute his annual gross volume of business upon the actual gross amount of business transacted by him during the first month of his engaging in such business, multiplied by the number of months of the current license year remaining, or multiplied by twelve (12) for the first full license year he engages in business, as the case may be.

(c) Every person, subject to the payment of the tax hereby imposed, who engages in a business temporary, seasonal or itinerant by its nature, shall compute his annual gross volume of business upon the actual gross amount of business transacted by him during such license year.