a
(a)
Magnetic permeability of free space $=4 \pi \times 10^{-7} NA ^{-2}$
The dimension of force is $\left[ MLT ^{-2}\right]$
The dimension of current is $\left[ T ^{-1} Q \right]$
Hence, the dimension of magnetic permeability of free space is $= N / A ^2=$
$\left[ MLT ^{-2}\right]\left[ T ^{-1} Q \right]^{-2}$
$=\left[ MLT ^{-2}\right]\left[ T ^{-1} Q ^{-2}\right.$
$=\left[ MLQ ^{-2}\right]$