La Chaussette Perdue is a Parisian self-service laundry, just two blocks from Sacré-Coeur. The operating costs per wash cycle are €2.00 for electricity and water. La Chaussette charges €3.50 per wash cycle. A dryer uses €0.40 worth of electricity to run for one ten-minute cycle, and La Chaussette charges €1.00 for a dryer cycle.

Paris being Paris, maintenance, rent and other fixed costs amount to €6,600 per month. The average customer does one wash cycle and three dryer cycles. How many customers does it take per month to break even?