Perpetual inventory using FIFO

Beginning inventory, purchases, and sales for Item Zeta$9$ are as follows:

Oct. $1$ Inventory $72$ units @ $$19$

Oct. $7$ Sale $51$ units

Oct. $15$ Purchase $61$ units @ $$22$

Oct. $24$ Sale $29$ units

a$.$ Cost of goods sold on October $24$

b$.$ Inventory on October $31$