I'm really confused about the last one the receivable turnover ratio, i just need the explanation for only this one

The following transactions were completed during December 2020 : cost of sales was $35,000. December 12 Collected cash for half of the credit sales made on December 5. December 20 Collected $90,000 in cash from customers for credit sales made in November 2020. December. The full amount was considered uncollectible. Imalda uses the aging of accounts receivable method to determine bad debt expense. The aging schedule at December 31,2020 , gives the following information about the accounts receivable estimated uncollectible: 1. Prepare the journal entries to record the transactions that occurred in December 2020 . (If no entry is required for a transaction/event, select "No journal entry required" in the first account fleld.) 2-a. Using the aging schedule, compute the bad debt expense for December 2020. 2-b. Prepare the journal entry to record bad debt expense for December 2020. (If no entry is required for a transaction/event, select "No journal entry required" in the first account fleld.) Answer is complete and correct. 3. Compute the gross profit percentage and the receivables turnover ratio for December 2020 . (Round the final answers to 2 decimal places.) Answer is complete but not entirely correct