Closing inventory valuation

Could someone kindly remind me of how to value closing inventories?

I am doing a question where I was required to value closing inventory (BPP Study text page 375)

It says

Closing inventories were counted and amounted to $388m at cost. However, shortly after the year end out-of-date inventories with a cost of $21m were sold for $14m.

As an answer closing inventories can be obtained

$(388m-(21m-14m))=$381m

I understood that inventories are valued at the lower of cost and NRV?

I would appreciate your advice.