Any individual sixty-five years of age or older or who, for federal income tax purposes, is blind may claim an exemption in an amount specified in Subsections A through C of this section not to exceed eight thousand dollars ($8,000) of income includable except for this exemption in net income. Individuals having income both within and without this state shall apportion this exemption in accordance with regulations of the secretary:
A. for married individuals filing separate returns, for any taxable year beginning on or after January 1, 1987:
B. for heads of household, surviving spouses and married individuals filing joint returns, for any taxable year beginning on or after January 1, 1987:
C. for single individuals, for any taxable year beginning on or after January 1, 1987: