请问这个12月31日outstanding的480000是什么？

问题如下：

The following table shows changes to the number of common shares outstanding for a company during 2012:

选项：

A.315,000.00

B.215,000.00

C.430,000.00

解释：

C is correct. The weighted average number of shares outstanding is time weighted:

A is incorrect. It fails to make the stock split retroactive to the beginning of the year: [(180,000 × 5) + (240,000 × 2) + (480,000 × 5)]/12 = 315,000.

B is incorrect. It does not take the stock split into account: [180,000 × (5/12)] + [240,000 × (7/12)] = 215,000.