I've seen a few examples like this, but I still don't understand the math on it, please explain with answer :)

FIFO and LIFO Costs Under Perpetual Inventory System

The following units of an item were available for sale during the year:

Beginning inventory	20 units at $48
Sale	16 units at $72
First purchase	27 units at $49
Sale	19 units at $73
Second purchase	25 units at $50
Sale	13 units at $74

The firm uses the perpetual inventory system, and there are 24 units of the item on hand at the end of the year.

a. What is the total cost of the ending inventory according to FIFO? $

b. What is the total cost of the ending inventory according to LIFO?

$