LIFO because, carried, period

cyber21

Beginning inventory=0

Quarter Purchases Sales
========= ========== =========
Qtr1 40 units at $30 13 units at $35
Qtr2 20 units at $40 35 units at $45
Qtr3 90 units at $50 60 units at $60

A) calculate the firm's inventory value at the end of the period using the FIFO,LIFO and Weighted Average inventor cost flow assumptions.

I am not clear on the way Schweser calculated LIFO.

During Qtr-2, the firm forced to sell Qtr-1 inventory of 15 units that carried over from Qtr-1 because 35 units sold in Qtr-2 where purchases only 20 units.

eagles_dare13

Inventory value using LIFO: $1,280.

What 3 options are given as the potential answers? And what don't you understand?