1. The problem statement, all variables and given/known data If A has a mass of 300kg, determine the mass of B if the system in figure P4-28 is to be in balance. (What I couldn't understand is the 2Tb in the answer.) 2. Relevant equations ΣFy=0 3. The attempt at a solution Since the pulley on top is connected with two pulley at the bottom, its force is doubled?