please explain solution

Littleton Books has the following transactions during May. May 2 Purchases books on account from Readers Wholesale for $3,000, terms 3/10,n/30. May 3 Pays cash for freight costs of $170 on books purchased from Readers. May 5 Returns books with a cost of $300 to Readers because part of the order is incorrect. May 10 Pays the full amount due to Readers. May 30 Sells all books purchased on May 2 (less those returned on May 5) for $3,700 on account. Assume that payment to Readers is made on May 24 instead of May 10. Record this payment. (If no entry nsaction/event, select "No Journal Entry Required" in the first account field.) Journal entry iworksheet Record payment of the full amount due to Readers. Note: Enter debits before credits