28:43 I'm kinda confused, why we are getting zero vector here, shouldn't it be vector 3, -1  https://matrixcalc.org/en/#%7B%7B1,2%7D,%7B3,6%7D%7D%2A%7B%7B3%7D,%7B-1%7D%7D####[['zero vector ', 'Mathematical_Related_Concept', 'NEU'], ['vector 3, -1 ', 'Mathematical_Related_Concept', 'NEU']]