A nonresident may claim and shall include only the part attributable to Maryland, as determined under this section, of: the subtractions from federal adjusted gross income under § 10-208 of this subtitle; the deduction for exemptions under § 10-211 or § 10-212 of this subtitle; and the standard deduction under § 10-217 of this subtitle; or itemized deductions under § 10-218 of this subtitle. Unless the Comptroller requires or allows another method to compute the items listed in subsection (a) of this section, a nonresident shall prorate the items using a fraction: the numerator of which is the Maryland adjusted gross income of the nonresident; and the denominator of which is the federal adjusted gross income of the nonresident.