The heavy-nūn active paradigm has different suffix handling across persons. لَيَبِيعَنَّ is third-person masculine singular, while لَتَبِيعِنَّ belongs to the addressed feminine singular.
PositionActive with heavy nūn
هُوَلَيَبِيعَنَّ
هُمَا (م)لَيَبِيعَانِّ
هُمْلَيَبِيعُنَّ
هِيَلَتَبِيعَنَّ
هُمَا (ف)لَتَبِيعَانِّ
هُنَّلَيَبِعْنَانِّ
أَنْتَلَتَبِيعَنَّ
أَنْتُمَا (م)لَتَبِيعَانِّ
أَنْتُمْلَتَبِيعُنَّ
أَنْتِلَتَبِيعِنَّ
أَنْتُمَا (ف)لَتَبِيعَانِّ
أَنْتُنَّلَتَبِعْنَانِّ
أَنَالَأَبِيعَنَّ
نَحْنُلَنَبِيعَنَّ
Dual forms retain their specific alif-related structure, and masculine plurals show a different adjustment. One singular-ending formula cannot simply be applied unchanged to every person.