Let A be an n X m matrix and B be an m x n matrix. For a square matrix. For a square matrix D. let Tr(D) denote trace of D, D] denote the determinant of D. Suppose that AB is invertible. Then which of the following is/are always true? (a) TrAB)= Tr(BA) (c)mzn. b) AB |BA| (d) BA must be invertible. (CMI-2014) Solution: (a, e) .