Assertion: Unit of torque is joule.

Reason: Unit of torque should be $\mathrm{N} \mathrm{m}$ and that is called joule.

Assertion: Velocity, volume and acceleration can be taken as basic variables.

Reason: All the three are independent of each other.

Assertion: If two physical quantities have the same dimensions, then they can be certainly added or subtracted.

Reason: If the dimensions of both the quantities are same then both the physical quantities should be similar.

The dimensions of ${\left[{\mu }_0{\in }_0\right]}^{-1/2}$ is :