Steps for

Example $1$: Consider a communication system with three independent units such as transmitting unit, receiving unit and a processing unit.

For the communication system to work, all the transmitting unit, receiving unit and processing unit must work.

$*$Assume that the transmitter has a constant failure rate of ${}_T=0\mathrm{.}002$ per hour, the receiver has a constant failure rate of ${}_R=0\mathrm{.}005$ per hour, and the processor has a constant failure rate of ${}_P=0\mathrm{.}008$ per hour.

Calculate the system reliability for a mission of $25$ hours.