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

Oct. $1$ Inventory $51$ units @ $$18$

$7$ Sale $34$ units

$15$ Purchase $46$ units @ $$19$

$24$ Sale $21$ units

Assuming a perpetual inventory system and using the first$-$in$,$ first$-$out $($FIFO$)$ method, determine $($a$)$ the cost of the goods sold on October $24$ and $($b$)$ the inventory value on October $31.$

a$.$ Cost of the goods sold on October $24$ $fill in the blank $1$

b$.$ Inventory value on October $31$ $fill in the blank $2$