Limiting reagent is PbCl2.
Amount of Pb3(PO4)2 formed:
\( \text{mmol of Pb}_3(\text{PO}_4)_2 = \frac{\text{mmol of PbCl}_2 \text{ reacted}}{3} = 24 \text{ mmol} \)
Among the following, choose the ones with an equal number of atoms.
Choose the correct answer from the options given below:
Let \( S = \left\{ m \in \mathbb{Z} : A^m + A^m = 3I - A^{-6} \right\} \), where
\[ A = \begin{bmatrix} 2 & -1 \\ 1 & 0 \end{bmatrix} \]Then \( n(S) \) is equal to ______.