The proportionality constant μ₀/4π in the Biot–Savart law has the exact SI value:

1. The permeability of free space is $\mu_0 = 4\pi \times 10^{-7}$ T m A⁻¹. 2. The Biot–Savart constant is $\dfrac{\mu_0}{4\pi}$. 3. Dividing: $\dfrac{4\pi\times10^{-7}}{4\pi} = 10^{-7}$ T m A⁻¹. 4. The $4\pi\times10^{-7}$ option is $\mu_0$ itself, not $\mu_0/4\pi$. _Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", p.144_