Magnetic Field of Straight Wires question from MHT CET 2024 (11 May, Shift 2)

Answer: (c)

1. NP is semi-infinite ending directly above C at distance $r$: $\frac{\mu_0}{4\pi}\frac{I}{r}$, out of the page.
2. Semicircular arc PQ (anticlockwise): $\frac{\mu_0 I}{4r} = \frac{\mu_0}{4\pi}\frac{I}{r}\pi$, out of the page. The radial part to C gives zero.
3. $B = \frac{\mu_0}{4\pi}\frac{I}{r}(1 + \pi)$
4. So the answer is (c).