Consider the complexes $\left(\mathrm{I}\right) {\mathrm{Co}}_2{\left(\mathrm{CO}\right)}_8 \left(\mathrm{II}\right) {\mathrm{Mn}}_2{\left(\mathrm{CO}\right)}_{10}$. The sum of metal-metal bonds in (I) and (II) is equal to ‘X’. The sum of bridged carbonyl groups in (I) and (II) is ‘Y’. Product of ‘X’ and' Y' is equal to

• A

  Zero

• B

  4

• C

  2

• D

  8