Enery saving

[NEILDR666]

I have been aske to provide the kWh saving on an annual basis on the following scenario: for a pre selection interview and am struggling with this one, any help would be greatly appreciated:

Q3. An air handling unit has been downrated from 5,000 to 4,300 cubic meters per hour. What annual saving in heating fuel should result if heat is supplied at 75% efficiency and the weather is 2,000 heating degree days per year? A) 15,000 kWh

B) 20,000 kWh

C) 8,000 kWh

D) 11,000 kWh

E) 65,000 kWh

F) 0 kWh

Please show all calculation formulas used.