Premise: (The jump in the penalty from having a child is mainly due to the fact that a single parent making $23,750 gets a $500 earned-income tax credit, while a couple making $46,700 is ineligible for that credit.)

Hypothesis: Jump in the child rearing penalty is not due to the fact that a single parent with a specific income earns a larger tax credit than a couple with a larger income.
Relation: contradiction