EX $7-12$ Periodic inventory by three methods OBJ. $2,4$

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

Jan. $1$ Inventory $1,000$ units at $$120$

Feb. $17$ Purchase $1,375$ units at $$128$

July $21$ Purchase $1,500$ units at $$136$

Nov. $23$ Purchase $1,125$ units at $$140$

There are $1,200$ units of the item in the physical inventory at December $31.$ The periodic

inventory system is used. Determine the inventory cost by $($a$)$ the first$-$in$,$ first$-$out method;

$($b$)$ the last$-$in$,$ first$-$out method; and $($c$)$ the weighted average cost method.