As an energy engineer at your company, you find 12 large exhaust fans constantly running to exhaust general plant air (no localized heavy pollution). They are each powered by 30 kW electric motors with loads of 34 kW each. You find they can be turned off periodically with no adverse effects. You place them on a central timer so that two of them are turned off for 10 minutes each hour. At any time, two of the fans are off, and the other ten fans are running. The fans operate ten h/day, 340 days/year. By using the following costs, answer each question.

* Demand charge: 10 USD/kW/month

* Energy charge: 0.08 USD/kWh

a) What is the annual demand saving in USD?

b) What is the annual energy saving in USD?

c) What is the total saving in USD?