For purposes of this paragraph, marital status shall be determined under section 7703.
The amount of the credit allowed under this subsection shall not be treated as a credit allowed under this subpart and shall reduce the amount of credit otherwise allowable under subsection (a) without regard to section 26 (a)(2) or subsection (b)(3), as the case may be. For purposes of subparagraph (B), any amount excluded from gross income by reason of section 112 shall be treated as earned income which is taken into account in computing taxable income for the taxable year.
Any increase determined under the preceding sentence shall be rounded to the nearest multiple of $50.