Answer: Option C
Volume of the cuboid :
$$\eqalign{
& = \left( {9 \times 8 \times 6} \right){\text{ c}}{{\text{m}}^3} \cr
& = 432{\text{ c}}{{\text{m}}^3} \cr} $$
Volume of the cube :
$$\eqalign{
& = \left( {\frac{1}{2} \times 432} \right){\text{ c}}{{\text{m}}^3} \cr
& = 216{\text{ c}}{{\text{m}}^3} \cr} $$
$$\eqalign{
& {a^3} = 216 \cr
& a = \root 3 \of {216} \cr
& a = 6 \cr
& 6{a^2} = 6 \times {6^2} \cr
& 6{a^2} = 216 \text{ cm}^2 \cr} $$