1. The problem statement, all variables and given/known data A force of magnitude 9.00 N pushes three boxes with masses m1 = 1.30 kg, m2 = 2.80 kg, and m3 = 4.90 kg Find the magnitude of the contact force between boxes 1 and 2. 2. Relevant equations Fnet,x = ma? 3. The attempt at a solution I thought that it would be 9.00 N, since the boxes are back-to-back-to-back, but that answer is wrong.