Mr. Potter plans to build a condominium building where each unit costs $150,000 to build. The demand for units is listed in a table showing 7 people willing to pay $200,000, 2 people $190,000, 5 people $180,000, 3 people $170,000 and 6 people $160,000. To maximize profit, the number of units Mr. Potter should build is 7.