the sum of— (i) the earned taxable income of such child, plus (ii) the amount in effect under subsection (h)(12)(B)(iv) for the taxable year. (4) Earned taxable income For purposes of this subsection, the term earned taxable income means, with respect to any child for any taxable year, the taxable income of such child reduced (but not below zero) by the net unearned income of such child.