January $20$ Purchased $400$ units @ $$4=$ $ $1,600$

April $21$ Purchased $130$ units @ $$6=780$

July $25$ Purchased $250$ units @ $$8=2,000$

September $19$ Purchased $100$ units @ $$10=1,000$

During the year, The Shirt Shop sold $720$ T$-$shirts for $$15$ each.

it says to find the fifo, lifo and the weighed average. Then says to find the gross margin for all three as well