The affix laṭ (Present Tense) comes optionally after a verb in denoting past time, in reply to an interrogation, when the words na 'not' and nu 'what of that' are in connection with it.,
As, अकार्षीः कटं देवदत्त -- न करोमि भोः or नाकार्षम्; -- अहं नु करोमि or अहं न्वकार्षम् 'Devadatta, did you make the mat ? -- No I did not; -- what of that, I did'.,