$18.$ Feed Tank $3,$ an atmospheric tank, is used solely to make Super Grade X$,$ which the plant makes $27$ times a year. The batch cycle for Super Grade X is $14$ hours, and feed from Feed Tank $3$ lasts for three hours each batch. A regulated nitrogen line to Feed Tank $3$ prevents the tank from being sucked in during the transfer. For a scenario where a regulator failure on the nitrogen line is the cause of a catastrophic tank failure, what is the factor for time at risk $($on an annual basis$)?$

a$.0\mathrm{.}00066$

b$.0\mathrm{.}0092$

c$.0\mathrm{.}074$

d$.0\mathrm{.}21$