Suppose a Given Control Unit Fails, on Average, Every 12,000

Multiple Choice

Suppose a given control unit fails, on average, every 12,000 hours. It takes an average of 900 hours to repair and reboot this unit. The repair/reboot procedures for this unit are being reconfigured. By how much would average repair/reboot time need to be reduced to increase availability by 5 percent (assuming the control unit's average life remains unchanged) ?

A) not more than 200 hours
B) more than 200 hours but not more than 400 hours
C) more than 400 hours but not more than 600 hours
D) more than 600 hours but not more than 800 hours
E) more than 800 hours