Three point charges are located at the corners of an equilateral triangle with a side of 0.5m, as shown below a) calculate the net electric force on the 7.0hc charge. b) how would the answer change if both the lower charges have their signs flipped (but are unchanged in magnitude)?

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