How far will 350 joules raise a 7kg mass? can you explain the formula used.

When an object gets raised to a higher place, it gets potential energy.
The energy has to come from whatever motor or person is lifting it.

The amount of potential energy it has is

   (mass of the object) x (acceleration of gravity) x (how far it gets lifted).

If the object has 7 kg of mass, and you have 350 joules of energy
to lift it with, then

       Potential energy at the top = 350 joules

              350 joules = (7 kg) x (gravity) x (height)

                             =  (7 kg) x (9.8 m/s²) x (height)

             (350 joules) / (7 kg x 9.8 m/s²)  =  height

               Height = (350) / (7 x 9.8)    (kg-m²/s²)  /  (kg-m/s²)

                         =    5.1 meters

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