What is the second cooler layer of ocean water?

When applying kirchhoff's rules, one of the essential steps is to mark each resistor with plus and minus signs to label how the electric potential changes from one end of the resistor to the other. the circuit in the drawing contains four resistors, each marked with the associated plus and minus signs. however, one resistor is marked incorrectly. which one is it?

To do work, this truck uses energy stored in chemical fuel and an electrical battery. how much total energy does this truck put out?

Does current flow through or across a resistor?