Is expiation obligatory for a nine-year-old son who did not fast for five days?

A child is not required to offer expiation if he breaks his fast, because the pen is lifted from him until he reaches puberty, and his fasting is supererogatory. As for the menstruating woman, breaking the fast is her ruling; she is not permitted to fast, and she must make up the missed days. Expiation suffices for those who are unable to fast due to an illness or old age from which recovery is not expected.