$\mathrm{A}=\left[\begin{array}{lll}5 & 0 & 0 \\0 & 6 & 0 \\0 & 0 & 7\end{array}\right]$ হলে $\mathrm{A}^{-1}=\text { ? }$

$\left[\begin{array}{ccc}\frac{1}{7} & 0 & 0 \\0 & \frac{1}{6} & 0 \\0 & 0 & \frac{1}{5}\end{array}\right]$

$\frac{1}{210}\left[\begin{array}{lll}5 & 0 & 0 \\0 & 6 & 0 \\0 & 0 & 7\end{array}\right]$

$\left[\begin{array}{lll}\frac{1}{5}&0&0\\0&\frac{1}{6}&0\\0&0&\frac{1}{7}\end{array}\right]$

$\frac{1}{210}\left[\begin{array}{lll}\frac{1}{5} & 0 & 0 \\0 & \frac{1}{6} & 0 \\0 & 0 & \frac{1}{7}\end{array}\right]$