Roger, dealing in second-hand pianos of different makes and models, uses the FIFO cost-flow assumption to ascertain the cost of unsold inventory. This would be wrong because:
(a) This is not the practice used by others in the trade
(b) Cost-flow assumptions may be used only when the items in the inventory are interchangeable
(c) The profit for the accounting period will be overstated
(d) It is not possible to sell each piano in the sequence in which they were purchased