Choose the One Alternative That Best Completes the Statement or Answers

Choose the one alternative that best completes the statement or answers the question.
- $$\begin{array} { l } R _ { 2 } = - 2 r _ { 2 } + r \\{ \left[ \begin{array} { r r r | r } 2 & 4 & 6 & - 8 \\1 & 2 & 3 & 6 \\4 & 6 & 7 & 1\end{array} \right] }\end{array}$$

A) $\left[ \begin{array} { l l l | r } 2 & 4 & 6 & - 8 \\ 0 & 0 & 0 & - 20 \\ 4 & 6 & 7 & 1 \end{array} \right]$

B) $\left[ \begin{array} { r r r | r } 2 & 4 & 6 & - 8 \\ - 4 & - 8 & - 12 & - 20 \\ 4 & 6 & 7 & 1 \end{array} \right]$

C) $\left[ \begin{array} { r r r | r } 2 & 4 & 6 & - 8 \\ 0 & 0 & 0 & 0 \\ 4 & 6 & 7 & 1 \end{array} \right]$

D) $\left[ \begin{array} { r r r | r } 2 & 4 & 6 & - 8 \\ - 4 & - 8 & - 12 & 6 \\ 4 & 6 & 7 & 1 \end{array} \right]$