14. Two blocks connected by a light horizontal rope is at rest on a horizontal, frictionless floor. Block A has a mass of 15.0 kg and B has a mass of 'm' kg. A constant horizontal force F = 60.0 N is applied to block A. In the first 5.00 s after the force is applied, block A moves 18.0 m to the right. (a) While the blocks are moving, what is the tension in the string connecting the two blocks? (b) What is the mass of the block B?