Write the proportionality constant of the Biot-Savart law with its unit and value (magnitude).

(N/A) The Biot-Savart law is expressed as $dB = \frac{\mu_0}{4\pi} \frac{I dl \sin \theta}{r^2}$.
The proportionality constant in this law is $\frac{\mu_0}{4\pi}$.
The value of this constant is $10^{-7} \ T \cdot m/A$ (or $10^{-7} \ Wb/(A \cdot m)$).
The $SI$ unit of this constant is $T \cdot m/A$ or $N/A^2$.