Revenue Pack-Em-In Real estate is building a new housing development. The more houses it builds, the less people will be willing to pay, due to crowding and smaller lot sizes. In fact, if it builds 40 houses in this particular development, it can sell them for $200,000 each, but if it builds 60 houses, it will only be able to get $160,000 each. Obtain a linear demand equation and hence determine how many houses Pack-Em-In should build to get the largest revenue. What is the largest revenue?