If an industry invests x thousand labor-hours, 11 x21, and Sy million, 1 sy2, in the production of N thousand units of a certain item, then N is given by the following formula. N(x,y) = x0.80y0.20 What is the average number of units produced for the indicated ranges of x and y? Set up a double integral and evaluate it. The average number of units produced for the indicated ranges of x and y is approximately (Do not round until the final answer. Then round to three decimal places as needed.) thousand units.