$A=\left[\begin{array}{c}4 \\2 \\-7\end{array}\right]$ এবং $B=\left[\begin{array}{lll}1 & -2 & -3\end{array}\right]$ হলে $AB =$ কত?

$\text { [21] }$

$\left[\begin{array}{lll}4 & -4 & 21\end{array}\right]$

$\left[\begin{array}{c}4 \\-4 \\21\end{array}\right]$

$\left[\begin{array}{rrr}4 & -8 & -12 \\2 & -4 & -6 \\-7 & 14 & 21\end{array}\right]$