Four steps are needed to create and deliver a service. After collecting information on errors per step, the reliabilities for each step are the following. Step $1$ is $0\mathrm{.}95.$ Step $2$ is $0\mathrm{.}99.$ Step $3$ is $0\mathrm{.}94.$ Step $4$ is $0\mathrm{.}92.$ With this information, the reliability of the total service system can be calculated as

$0\mathrm{.}87$

$0\mathrm{.}81$

$0\mathrm{.}84$

$0\mathrm{.}91$