$(5$ points$)$ A systems safety team examined the likelihood of loss of steam to a critical production process in the facility. The steam is generated by electrical turbine by compressing vaporized water. Electricity is produced through the electrical grid and through a backup diesel generator should loss of electricity from the grid occur.

The overall steam system failure is due to the loss of electricity or water supply. For the electrical failure to occur, a failure of the electrical grid $($MTBF $($:$=2\mathrm{.}2{10}^{5}hr\frac{s}{f}$ail$\}$ AND a failure of the backup generator $($MTBF $=1\mathrm{.}5{10}^{5}hr\frac{s}{?}$ fail$)$ must occur at the same time. For the water supply to fail, electrical failure should occur $($Grid and Backup both must fail$),$ the water filter $($MTBF $=9$ X ${10}^{5}hr\frac{s}{?}$ fail$)$ is clogged, $O{R}_{?}$ the water pump is down $($MTBF $=6\mathrm{.}2{10}^{4}hr\frac{s}{?}$ fail