Two identical circular loops A and B, each of radius R, are arranged coaxially with their centres R apart. Loop A carries a current I clockwise when viewed from above, while loop B carries the same current I anticlockwise.
a. (i) State the direction of the magnetic field produced by loop A at the midpoint of the line joining the two centres.
b. (ii) State the direction of the magnetic field produced by loop B at the same point.
c. (iii) Hence determine the direction and relative magnitude (zero, equal to one loop, or double) of the net magnetic field at the midpoint. Justify your answer briefly.