The na of hinu and mīnā is changed to ṇa , when coming after an upasarga containing in it a cause of change.,
Thus प्रहिणोति, प्रहिणुतः, प्रमीणाति, प्रमीणीतः ॥ The root हि belongs to Svadi class of verbs and takes the vikarana नु technically श्नु; and the root मी belongs to Kryadi class which takes the vikarana श्ना ॥ In the sutra the verbs are shown with the vikaranas affixed. Under certain circumstances the forms of the vikarana is changed from नु to नो and ना to नी, but the rule still applies, because the substitute of an अच् or vowel is like the principal. See (l. I. 57).,