Describe the LIFO double-extension method. Using the following information compute the index at December 31, 2010, applying the double-extension method to a LIFO pool consisting of 25500 units of product A and 10,350 units of product B, the base-year cost of product A is $10.20 and of product B is $37.00. The price at December 31, 2010, for product A is $21.00 and for product B is $45.60.