The three valuation methods are (1) LIFO (2) FIFO (3)Weighted Average. (use of ACTUAL costs)
Standard cost is used as an alternative to cost layering systems such as LIFO and FIFO (uses ESTIMATED cost)
Inventories should be measured at the lower of cost or net realizable value (NRV). NRV is only a floor/ceiling to be considered in valuing and revaluing inventories.