According to Rule 9(b) of the Good Conduct Prisoners Probational Release Rules, 1927, what is the maximum age of a prisoner at the time of their most recent sentence to qualify for conditional release?

Explanation

Rule 9(b) specifies that prisoners whose age does not exceed twenty-one years at the time of their latest sentence are eligible for conditional release under the Good Conduct Prisoners Probational Release Rules, 1927.