A metal complex with a formula $\mathrm{MCl}_4 \cdot 3 \mathrm{NH}_3$ is involved in $\mathrm{sp}^3 \mathrm{~d}^2$ hybridisation. It upon reaction with excess of $\mathrm{AgNO}_3$ solution gives ' $x$ ' moles of AgCl . Consider ' $x$ ' is equal to the number of lone pairs of electron present in central atom of $\mathrm{BrF}_5$. Then the number of geometrical isomers exhibited by the complex is _________.