Buckminsterfullerene contains the following $X$ number of six-membered and $Y$ number of five-membered rings. What is the value of $X$ and $Y$?

• A
  $X=10, Y=12$
• B
  $X=15, Y=15$
• C
  $X=20, Y=12$
• D
  $X=10, Y=20$