(2) The income of a business firm that is exempt under this section shall be determined by multiplying the taxable income of the business firm (as determined before application of this section) by the sum of:
(a) 50 percent of the ratio of the payroll of the business firm from employment at the certified facility over total statewide payroll of the business firm, as determined under ORS 314.660; and
(b) 50 percent of the ratio of the average value of the property of the business firm at the certified facility over the average value of the property of the business firm statewide, as determined under ORS 314.655.
(3) The sum computed under subsection (2) of this section shall be the amount of the business firm’s income that is exempt from tax under this chapter.
(4) As used in this section:
(a) "Business firm" has the meaning given that term in ORS 285C.500.
(b) "Certified facility" means a facility, as defined in ORS 285C.500, for which an annual certification under ORS 285C.506 has been issued. [2001 c.944 §8]