The augment nuk (n) comes after the reduplicates of car and phal in the Intensive (with expressed or elided yaṅ).,
Thus चंचूर्यते and चंचूरीति (the lengthening of ऊ is by 8.2.77) पंफुल्यते and पंफुलीति ॥ See the following sutra.,
चर-फलोश् च
Adhyāya 7 · Pāda 4 · Rule 87