Two long, parallel conductors are 4.0cm apart and carry currents of 20A and 30A in the same direction. What is the magnitude of the net magnetic field at a point midway between the wires? $
\left(\mu_0 = 4\pi\times10^{-7}\,\text{H\,m}^{-1}\right)$
a) 5×10−4T
b) 5×10−5T
c) 1×10−4T
d) 2.5×10−4T