According to the principal of prudence At what cost inventory should be valued if net realisable value of the invtry is lower than cost or vise versa?

inventory is valued at lower of cost or net realisable value as per IAS2.

Inventory should  be valued at cost price or market price, whichever is lower

Inventory must be valued at Cost or Market value whichever is lower. This is as per the IAS issued by the Institute of Chartered Accountant of India and in IFRS also the same.

at the lower of cost or NRV

The  lower of cost or market method of valuation is recommended.