Vernon Inc. has analyzed the setup time on its computer$-$controlled lathe. The setup requires changing the type of fixture that holds a part. The average setup time has been $140$ minutes, consisting of the following steps:

Turn off machine and remove fixture from lathe $15$ minutes

Go to tool room with fixture $15$

Record replacement of fixture to tool room $18$

Return to lathe $20$

Clean lathe $20$

Return to tool room $20$

Record withdrawal of new fixture from tool room $12$

Return to lathe $15$

Install new fixture and turn on machine $5$

Total setup time $140$ minutes