explain these please, need extra notes. Thank you.

a. Inventory markdowns i. LCNRV ii. LCM b. Methods of estimating inventory i. Gross Profit ii. Retail method iii. Conventional retail method 1. Know how to calculate impact of markups and markdowns iv. Applying RIM/Conventional RIM under 1. Average 2. LIFO 3. Dollar Value LIFO c. Change in inventory methods i. Retrospective versus prospective treatment d. Inventory errors i. Impact on COGS, NI, RE, etc... ii. Correcting inventory errors e. Purchase commitments