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**learningguy** The problem states that there are two blocks of masses, m1 = 4.00 kg and m2 = 3.00kg, which are placed in contact with each other on a frictionless horizontal surface. A constant force F = 9.00N is applied to the block of mass m1, a) Determine the magnitude of the acceleration of the two-block system, and b) Determine the magnitude of the contact force, P12, between the two blocks.

A is simple a=EF/M = 9N/7KG = 1.29m/s^2 but I cant figure out what formula to use for b although it seems like it should be pretty simple. Any help would be much appreciated.