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\hat{V B} \hat{F}=\left[\begin{array}{cccc}\hat{V}_{1} & 0 & \cdots & 0 \\ 0 & \hat{V}_{2} & \cdots & 0 \\ \vdots & \vdots & \ddots & \vdots \\ 0 & 0 & \cdots & \hat{V}_{G}\end{array}\right]\left[\begin{array}{cccc}B_{11} & B_{12} & \cdots & B_{1 G} \\ B_{21} & B_{22} & \cdots & B_{2 G} \\ \vdots & \vdots & \ddots & \vdots \\ B_{G 1} & B_{G 2} & \cdots & B_{G G}\end{array}\right]\left[\begin{array}{cccc}\hat{F}_{1} & 0 & \cdots & 0 \\ 0 & \hat{F}_{2} & \cdots & 0 \\ \vdots & \vdots & \ddots & \vdots \\ 0 & 0 & \cdots & \hat{F}_{G}\end{array}\right]