The pivot for the seat of a desk chair consists of the steel plate A, which supports the seat, the solid steel shaft B which is welded to A and which turns freely in the tubular member C, and the nylon bearing D. If the weight W of a scatted 80-kg person acts directly above the pivot, determine the magnitude of the couple M for which rotation of the seat is impending knowing that the coefficient of static friction is 0.15 between the tubular member and the bearing.

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D. в -24 mm- -30 m