Help with CFA Reading 26 Practice problem 2B

Not clear on the what rates to use under Temporal when solving for NonMonetary items such as COGS & Inventory. The solution in the CFA text shows FIFO COGS is divided by the historical rate and when LIFO COGS is divided by Average rate. Can someone explain why we are using different exchange rates. I thought we should be using historical for both LIFO & FIFO or the way Stalla is teaching is when using LIFO use the historical and when solving FIFO use Current or if purchases evenly throughout the year use Weigthed Avg. But dont why they are dividing FIFO COGS by historical and then dividing LIFO COGS by Weighted Average. So I am a little confused when to use the rates what when dealing COGS & INV with Temporal Method. If someone can please advise.

Problem 2B is on the errata. Please ignore last post.