Periodic Inventory by Three Methods

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

Jan. $1$ Inventory $10$ units at $$50$

Feb. $17$ Purchase $17$ units at $$52$

Jul. $21$ Purchase $11$ units at $$53$

Nov. $23$ Purchase $19$ units at $$55$

a$.$ Determine the inventory cost by the first$-$in$,$ first$-$out method.

b$.$ Determine the inventory cost by the last$-$in$,$ first$-$out method.