The mass of one cup of water is 0.236 kilograms. use scientific notation to represent the mass of one cup of water.

               Scientific Notation is a special way of writing numbers.
               The decimal point is placed after the first digit and it is followed by:
               x ( times )10 to a power that puts the decimal point where it should
               be.
                 0.236 kg = 2.36 * 10^(-1) kg 

Pe = 1/2k(x)^2  and .05n/m = .05x10^-9m = x 

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