Which statement is logically equivalent to "If Yoda cannot use a lightsaber, then he cannot help Luke win the battle."
Yoda cannot use a lightsaber and he will help Luke win the battle.
If Yoda can help Luke win the battle, then he can use a lightsaber.
Yoda can use a lightsaber if and only if he can help Luke win the battle.
Yoda cannot use a lightsaber and will not help Luke win the battle.