This excerpt taken from the AA DEF 14A filed Feb 26, 2007.
Column (k)Grant Date Stock Price
Represents the average of the high and low prices of the companys common stock on the January 12, 2006 grant date for stock options or performance stock options granted in 2006, as reported on the New York Stock Exchange, which is the method required under the 2004 Alcoa Stock Incentive Plan for grants made in 2006 and before. The closing price of the companys common stock on that date was $28.81. See CD&A on page 24, for a discussion of how the exercise price of stock options is determined.