The masses mA = 15 kg and mB = 30 kg, and the coefficients of friction between all of the...

The masses mA = 15 kg and mB = 30 kg, and the coefficients of friction between all of the surfaces are μs = 0.4 and μk = 0.35, the blocks are stationary when the constant force F is applied. Determine the resulting acceleration of block B if

(a) F = 200 N

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(b) F = 400 N.