Thanks for the question! You’re mixing up your necessary and sufficient clauses here. Remember, the third rule tells us that “L performs third ONLY IF N performs fifth.” X only if Y gets diagrammed
X —> Y
In other words, “only if” introduces the necessary, unlike “if,” which introduces the sufficient. So it should be diagrammed
L third —> N fifth
Which means that if N goes fifth, it doesn’t have to be true that L goes third. That’s a mistaken reversal.
Hope this helps! Feel free to ask any other questions that you might have.
