Text: Since then, Mir's main oxygen system has failed repeatedly (forcing its crew to burn chemical candles to survive), its commander has developed heartbeat irregularities (caused by stress), and a cosmonaut has accidentally unplugged its main computer (which is less powerful than the chip in some cellular phones).
Entailment: The main oxygen system of Mir has had repeated failures.
Contradiction: The main oxygen system of Mir has been remarkably steady and consistent.