Portable Video Cd Player Please Help Confused With Lifo,Fifo, And Average Cost Method Problem Using Perpetual Inventory System?

Please help confused with Lifo,Fifo, and average cost method problem using perpetual inventory system? - portable video cd player

I have no idea how to properly do so.
Inventory, purchases and sales of portable video CD are:
1. Inventory of April 50-25
5. April the sale of 40 units
14. April purchase of 60 units at $ 36
21. April the sale of 35 units
23. April in the sale of 10 units
30. May, buying 75 units at $ 38

The company has used a perpetual inventory system, cost of first in, first out, last in, first out "method and the average cost method. Determine the cost of goods sold for each sale and the remaining inventory after each sale . If you do simple math and please explain to me how you get these calculations step by step.