Hi, I need help with this similar problem and to make things short, I also found that
a = m3g/m2 from part b which states: Find the force F by ONLY using the separate free body diagrams of M2, M3, and M1+M2+M3.
so for M1+M2+m3 F=(M3g/M2)(M1+M2+M3)
but for my part c it says: Find the force F...