Perpetual inventory using FIFO

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

Oct. $1$ Inventory $79$ units @ $$24$

Oct. $7$ Sale $61$ units

Oct. $15$ Purchase $51$ units @ $$25$

Oct. $24$ Sale $24$ units October $31.$

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

b$.$ Inventory on October $31$