The answer is (b): the upper spring scale will read 10 Newtons, as seen in the photograph below.
When the free end of the rope is pulled, exerting a force of 10 Newtons on the lower spring scale, three additional force components are actually involved. Tension applied to the end of the rope is transmitted to both sides of the rope, so there is a force of twice the applied force on the lower spring scale. This means that in order to apply a force of 10 Newtons downward on the lower spring scale you must apply a force of 5 Newtons to the end of the rope. There is also a force of 5 Newtons pulling up on the lower part of the frame. The net force applied on the upper scale due to the pull at the free end of the rope is therefore 5+5-5=5 Newtons downward. This adds to the 5 Newton weight of the frame and its contents, causing a force of 10 Newtons on the upper scale when the lower scale reads 10 Newtons.
