A thin square conducting frame PQRS of side length a. the resistance of wire PQR is r and that of PSR is 2r. The value of the magnetic field at the center of the loop is found to be:
a) ( μ₀ i/2√2a )
b) ( μ₀ i/4√2a )
c) ( μ₀ i/8a )
d) ( μ₀ i/a )