This is just an electrical installations course. @phinds, you are correct - the fuses would be the blue rectangles by the switches. I understand what fuses do and I thought I needed: I (Amps) = P (Watts) ÷ V (Voltage) to figure it out...
(a) Calculate the size of Conductor and Fuse, the amount of Current through the conductor, Voltage ACROSS the existing LOAD and power consumed by the EXISTING LOAD under normal circuit condition (when the switch of the above circuit will be closed).
(b) Calculate the overload current...