Blocks A and B, weighing 7 and 15 lb, respectively, are released from rest when the spring...

Blocks A and B, weighing 7 and 15 lb, respectively, are released from rest when the spring is unstretched. If all sources of friction are negligible and k = 12 lb/ft, determine the maximum vertical displacement of B from the release position, assuming that A never leaves the horizontal surface shown and the cord connecting A and B is inextensible.

Figure P4.55