An electronics store stocks high-end DVD players, surround sound systems, and televisions. They have limited storage space and can stock a maximum of 210 of these three machines. They know from past experience that they should stock twice as many DVD players as stereo systems and at least 30 television sets. If each DVD player sells for $450, each surround sound system sells for $2000, and each television sells for $750, how many of each should be stocked and sold for maximum revenues? What is the maximum revenue?