Two blocks connected by a light horizontal rope sit at rest
on a horizontal, frictionless surface. Block A has mass 15.0 kg, and
block B has mass m. 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 T in the rope that connects the two blocks? (b) What
is the mass of block B?