Identify the group, then make only that group’s change.
● First: يَجْلِسُ ← لَنْ يَجْلِسَ — final dammah becomes fatḥah.
● Second, dual: يَكْتُبَانِ ← لَنْ يَكْتُبَا — final nūn is removed.
● Second, plural: يَقْرَؤُونَ ← لَنْ يَقْرَؤُوا — final nūn is removed.
● Third: يَكْتُبْنَ ← لَنْ يَكْتُبْنَ — no visible ending change.