This is a 3 part question and I've figured out the first two parts a and b, but cannot figure out the last part c.

Please help me with the following problem:

A company converted from the conventional retail method to the LIFO retail method on January 1, 2020, and is now considering converting to the dollar-value LIFO inventory method. During your examination of the financial statements for the year ended December 31, 2021, management requested that you furnish a summary showing certain computations of inventory cost for the past 3 years.

Here is the available information.

The inventory at January 1, 2019, had a retail value of $55,500and cost of $29,500based on the conventional retail method.

Transactions during 2019 were as follows.