Is the fasting of someone who was previously ignorant of the ruling, sufficient atonement for his oath, or not?

The expiation for an oath is feeding ten poor persons, or clothing them, or freeing a slave. Whoever is unable to do so should fast for three days. It is not permissible to resort to fasting except after being unable to perform the first three acts. If the questioner is able to feed ten poor persons or clothe them, then her consideration of fasting is not sufficient, and the expiation remains her responsibility until she fulfills it.