Take off your old tire and put on a new one!
"Who shall retire" is correct. When asking a question about a person, use "who." "Which" is used to refer to things or a specified group of people.
Retire
After years of hard work, John decided to retire and spend more time with his family.
The Undertaker will retire when he dies
She wasn't going to retire yet.They decided to retire to bed for the night.
the band did not retire
most can retire after 20 years.
Retire is a verb.
he didn't retire he got maried
when did sally ride retire
retire: jubilar(se)
he can resign not retire