September $1,$ the beginning of its fiscal year, Cullumber Ltd$.$ had an inventory of $106$ calculators at a cost of $$20$ each. The company s a perpetual inventory system. During September, the following transactions occurred:

$2$ Purchased $795$ calculators for $$20$ each from Digital Corp. on account, terms $\frac{n}{30}.$

$10$ Returned $21$ calculators to Digital for $$420$ credit because they did not meet specifications.

$11$ Sold $340$ calculators for $$30$ each to Campus Book Store, terms n $\frac{?}{30}.$ Management estimates returns of $4\%$ based on prior experience.

$14$ Granted credit of $$630$ to Campus Book Store for the return of $21$ 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.