Figure shows a thin metallic triangular sheet ABC. The mass of the sheet is M.The moment of inertia of the sheet about side AC is:

• A

  $\frac{{\mathrm{MI}}^2}{18}$

• B

  $\frac{{\mathrm{MI}}^2}{12}$

• C

  $\frac{{\mathrm{MI}}^2}{6}$

• D

  $\frac{{\mathrm{Ml}}^2}{4}$