Field due to a straight wire of infinite length is 4πrμ0i if the point is on a line perpendicular to its length while at the centre of a semicurcular coil is 4πrμ0πi
∴ B = Ba+Bb+Bc = 4πrμ0i + 4πrμ0πi + 4πrμ0i = 4πrμ0i (π + 2) out of the phase