In two different cases, two blocks are sliding to the right across a horizontal surface. In Case A the mass of each block is 3.9 kg. In Case B the mass of block 1 (the block behind) is 7.8 kg, and the mass of block 2 is 3.9 kg. No frictional force acts on block 1 in either Case A or Case B. However, a kinetic frictional force of 7.6 N does act on block 2 in both cases and opposes the motion. For both Case A and Case B determine
(a) the magnitude of the forces with which the blocks push against each other and
(b) the magnitude of the acceleration of the blocks.