Suppose your AC control unit fails, on average, every $10,000$ hours. It takes an average of $700$ hours to repair and reboot this unit. How much would the average repair$/$reboot time need to be reduced to increase availability by $5$ percent $($assuming the control unit's average life remains unchanged$)?$

more than $400$ hours but not more than $500$ hours

not more than $400$ hours

more than $600$ hours but not more than $700$ hours

more than $500$ hours but not more than $600$ hours

more than $700$ hours