Mathematics > algebra > Matrices

Four friends Abhay, Bina, Chhaya and Devesh were asked to simplify $4AB+3(AB+BA)-4BA,$ where $A$ and $B$ are both matrices of order $2\times2$. It is known that $A\ne B\ne I$ and $A^{-1}\ne B$. Their answers are given as: Abhay : $6AB$ Bina : $7AB-BA$ Chhaya : $8AB$ Devesh : $7BA-AB$ Who answered it correctly?