Harrison, Carla, and Fred are housepainters. Harrison and Carla can paint 100 square feet per hour using a standard paintbrush, and Fred can paint 80 square feet per hour. Any of the three can paint 200 square feet per hour using a roller. . Assume Harrison, Carla, and Fred have only paintbrushes at their disposal. What is the average labor productivity, in terms of square feet per painter-hour, for the three painters taken as a team?