What do Benedick and Beatrice tell each other when all the others leave?(Act 4)

Everyone agrees to the plan and leaves. Only Benedick and Beatrice remain behind. They both declare their love for each other and Benedick asks her to make him do anything to affirm how much he loves her. Beatrice famously replies, "Kill Claudio" (4.1.287). Benedick at first says he will never do such a thing, and Beatrice tells him he does not really love her then. She tries to leave, but Benedick repents his answer and stops her. He tells her that he will challenge Claudio for her.