在看CFA一级，存货这一章原书的practice里的43题，答案里说到：
Crux’s adjusted inventory turnover ratio must be computed using cost of goods sold (COGS) under FIFO and excluding charges for increases in valuation allowances.
但用到的公式是COGS (adjusted) = COGS (LIFO method) – Charges included incost of goods sold for inventory write-downs – Changein LIFO reserve
要减去change in LIFO reserve这没问题，关键是中间这一步有点糊涂了。。
首先解释里说的是excluding charges for increase in valuation allowance但是到了公式变成了charges included in cogs for write down，到底是啥呢应该？
然后啥是charges included in cogs for write down呢？从分录来看
跌价：Dr 资产减值损失Cr 存货跌价准备；出售：Dr COGS/存货跌价准备Cr 库存商品；这个write down和COGS不是两个东西么。。要咋了解包含在COGS里的write down？
其次我自己设立了一个场景，感觉应该是减掉write down的variation？有点不太能理解了，想了好久也没搞明白，希望有懂的老师帮忙解答下，跪谢啊～～～