Weston publishing publishes a deluxe edition and a standard edition of its spanish-english dictionary. weston's management estimates that the number of deluxe editions demanded is x copies/day and the number of standard editions demanded is y copies/day when the unit prices are p 20-0.009x 0.002y -20-0.002r-0.003 dollars, respectively (a) find the daily total revenue function r(x, y) (b) find the domain of the function r. the set of all points (x, y) with 20 0.009x 0.002y 2 0, 20 0.002x 0.003y 2 0 0, ye0 the set of all points (x, y) with x 2 the set of all points (x, y) with 20 - 0.009x-0.002y 0, 20-0.002x - 0.003y 20, x 20,y20 the set of all points (x, y) with 20-0.009x-0.002y 2 0, 20-0.002x-0.003y 0, x > 0, y > 0 the set of all points (x, y) with 20-0.009x - 0.002y> 0, 20-0.002x-0.003y > 0, x 20,y 2 0