Hey guys,

Got one question that is confusing me. For part b, the solution says that the force is 18.9 N downwards, but I don't understand how to calculate that?

From my understanding, the sum of all forces on A would be 10.5N upwards. I'm assuming that the sum of all forces on A would just be its weight force plus normal force, and that the normal force A experiences would be the force that B exerts on A. Letting upwards be positive, I would then assume 10.5 = -29.4+x, where x is the normal force that A experiences, or the magnitude of the force that A exerts on B. However, this gives a final answer 39.9 N downwards, could someone please explain this?