Consider the structure of ${\mathrm{Al}}_2({\mathrm{CH}}_3{)}_6$ compound and find the value of  $\mathrm{A} + \mathrm{B} +\mathrm{C}$

A = Maximum number of atoms in one plane

B = Total number of $2c-2e^{-}$ bonds

C = Total number of  ${\mathrm{sp}}^3$ hybridised atoms

Maximum number of atoms in one plane in of ${\mathrm{Al}}_2({\mathrm{CH}}_3{)}_6$ is 10. Here, total number of $2c-2e^{-}$ bonds are 22 while the total number of  ${\mathrm{sp}}^3$ hybridised atoms are 8. Thus,

$\mathrm{A}=10, \mathrm{B}=22, \mathrm{C}=8$

So,

$$\begin{gathered} \mathrm{A}+\mathrm{B}+\mathrm{C} \\ 10 + 22 + 8 = 40 \end{gathered}$$

Thus, the correct answer is 40.