Suppose an index has two firms in it, firm A and firm B. When the market closed yesterday, firm A's stock was selling at $10 a share with 100 shares outstanding, Firm B was selling at $20 a share with 5 shares outstanding. Today Firm A's closing price is $11 and B's closing price is $21. How much is the index's return over today if it is value weighted?

7.5%

9.55%

6.67%

10%