When Noon-e-I'raabi drops, two written patterns deserve special attention.
After LanBefore LanPattern
لَنْ يَفْعُلُوْايَفْعُلُوْنَmasculine plural
لَنْ تَفْعُلِيْتَفْعُلِيْنَfeminine Haadhir singular
In the masculine plural, the Noon disappears and an Alif is written after the final Waaw.
In the feminine Haadhir singular, the Noon disappears while the final Yaa remains.