If a woman begins menstruating after the time for Maghrib has entered by the amount of one rak'ah, is the 'Isha' prayer obligatory for her?

Question : Is the 'Isha' prayer obligatory for her if she catches the amount of one rak'ah with the imam?

Answer : Then she became confused and purified herself from menstruation. We say: make up the Maghrib prayer, that is clear. But do we say: make up the 'Isha' prayer? The answer is no. Why? Because she missed the 'Isha' prayer while she was menstruating, is that not so? And prayer is not obligatory for a menstruating woman.