On September $1,$ the beginning of its fiscal year, Cullumber Ltd$.$ had an inventory of $128$ calculators at a cost of $$20$ each. The company uses a perpetual inventory system. During September, the following transactions occurred:

Sept. $2$ Purchased $960$ calculators for $$20$ each from Digital Corp. on account, terms $\frac{n}{30}.$

$10$ Returned $32$ calculators to Digital for $$640$ credit because they did not meet specifications.

$11$ Sold $450$ calculat

$14$ Granted credit of $$960$ to Campus Book Store for the return of $32$ calculators that were not ordered. The calculators were restored to inventory.

$29$ Paid Digital the amount owing.

$30$ Received payment in full from the Campus Book Store.