A long wire with a square cross-section 13 cm on a side carries a current of 10 A that is uniformly distributed over the cross-section of the wire. What is the value of the integral along a square with side length 8 cm concentric with the wire and with sides parallel to those of the wire

Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current

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