I walked up to Malachi and asked him to go out to the back yard and pick up sticks and toss them into the burn pile. He said “okay, Daddy”, and then proceeded to go into his room and read a book about dump trucks.

I then walked up to Zachary and said “Zac, go out to the back yard and pick up sticks and toss them into the burn pile.” He said “NO!” and then ran into the kitchen and got himself something to eat. While he consumed a few grapes, he thought more about what I asked him, and promptly went out and began putting sticks in the burn pile. Meanwhile, Malachi was still upstairs, quietly reading his book.

Question: which son obeyed?