Blocks of mass 20, 80, and 240 kg are lined up from left to right in that order on a frictionless surface so each block is touching the next one. A rightward-pointing force of magnitude 39 N is applied to the left-most block.
1) What is the magnitude of the force that the left block exerts on the middle one? N
2) What is the magnitude of the force that the middle block exerts on the left one? N
3) What is the magnitude of the force that the middle block exerts on the rightmost one?