For an individual who is a nonresident or part-year resident of this state, multiply the amount calculated under subd. 35. a. or b., by a fraction the numerator of which is the individual’s wages, salary, tips, unearned income, and net earnings from a trade or business that are taxable by this state and the denominator of which is the individual’s total wages, salary, tips, unearned income, and net earnings from a trade or business. In this subd. 35. c., for married persons filing separately “wages, salary, tips, unearned income, and net earnings from a trade or business” means the separate wages, salary, tips, unearned income, and net earnings from a trade or business of each spouse, and for married persons filing jointly “wages, salary, tips, unearned income, and net earnings from a trade or business” means the total wages, salary, tips, unearned income, and net earnings from a trade or business of both spouses.