$1.$Prepare journal entries to record the purchase and sale transactions, as well as the cost of sales, assuming that all sales and purchase transactions are on account and that the weighted$-$average method is used. $($Do not round intermediate calculations and round the final answers to $2$ decimal places. If no entry is required for a transaction$/$event$,$ select $"$No journal entry required" in the first account field.$)$

a$)$ Record sales on account.

b$)$Record cost of sales on goods sold on account.

c$)$Record purchase of goods on account.

d$)$Record sales on account.

e$)$Record cost of sales on goods sold on account.

f$)$Record purchase of goods on account.

Assume that because of a clerical error, the ending inventory is reported to be $1,060$ units rather than the actual number of units $(1,160)$ on hand.

a$.$ If FIFO is used, calculate the amount of the understatement or overstatement in the cost of sales for the first six months of the current year.

b$.$ If FIFO is used, calculate the amount of the understatement or overstatement in the current assets at June $30$ of the current year.