(a) In each taxing entity the tax imposed by Subchapter D, Chapter 151, the tax imposed under Section 321.104(a), if applicable, and the tax imposed under Section 322.102 are added together to form a single combined tax rate, except in a situation described by Section 322.105(b).
(b) The formula prescribed by Section 322.103(b) applies to the computation of the amount of the tax under this section.