Four friends Abhay, Bina, Chhaya and Devesh were asked to simplify 4 AB +3( AB + BA )-4 BA, where A and B are both matrices of order 2 × 2. It is…

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