Three very long boards of equal masses are stacked on a horizontal surface as shown. The coefficients of friction for each pair of surfaces are shown (assume that for each pair of surfaces, the coefficients of static and kinetic friction are the same).

When the top board is given a strike to the right, the system comes to rest after time t. How long would it take the system to come to rest if the bottom board is struck instead? In both cases, the initial speed of the struck board is the same.

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