∵[V]=[b] ∴ Dimension of b=[L3] $\begin{aligned}
& &[\mathrm{P}]=\left[\frac{\mathrm{a}}{\mathrm{V}^2}\right] \
& {[\mathrm{a}]=\left[\mathrm{PV}^2\right]=\left[\mathrm{ML}^{-1} \mathrm{T}^{-2}\right]\left[\mathrm{L}^6\right]}
\end{aligned}Dimensionof\mathrm{a}=\left[\mathrm{ML}^5 \mathrm{T}^{-2}\right]\therefore \mathrm{ab}^{-1}=\frac{\left[\mathrm{ML}^5 \mathrm{T}^{-2}\right]}{\left[\mathrm{L}^3\right]}=\left[\mathrm{ML}^2 \mathrm{T}^{-2}\right]$