If $\mathbf{A}^{-1} = \begin{pmatrix} 4 & 6 \\ -2 & 10 \end{pmatrix},$ and $\mathbf{B} = \frac{1}{2} \mathbf{A},$ then find $\mathbf{B}^{-1}.$
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<|im_start|>user
If $\mathbf{A}^{-1} = \begin{pmatrix} 4 & 6 \\ -2 & 10 \end{pmatrix},$ and $\mathbf{B} = \frac{1}{2} \mathbf{A},$ then find $\mathbf{B}^{-1}.$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\begin{pmatrix} 8 & 12 \\ -4 & 20 \end{pmatrix}
If $\mathbf{A}^{-1} = \begin{pmatrix} 4 & 6 \\ -2 & 10 \end{pmatrix},$ and $\mathbf{B} = \frac{1}{2} \mathbf{A},$ then find $\mathbf{B}^{-1}.$
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