Some estimates for the cement industry sug- gest the following relationship between capa- city and average cost: Capacity (thousands of tons) Average cost 250 28.78 500 25.73 750 23.63 1,000 21.63 1,250 21.00 1,500 20.75 1,750 20.95 2,000 21,50 a. At what production level are scale economies exhausted? b. Calculate the scale economy index for the production levels 500, 750, 1,000, 1,500, and 1,750