Incomplete records

Sir i am not able to understand illustration 1 incomplete records in kaplan study text:
The closing trade receivables figure at 31 july 2018 taken from prior year’s statement of financial position was 98425 you have reviewed the list of receivables and calculated that receivables outstanding at 31 july 2019 total 107550 after discussion it was determined that prior to year end 1500 of trade receivables were written off as irrecoverable .this has not been reflected in the list of memorandum to assist one of your book keepers has reconciled the cash book with bank statement for the year and has calculated 245675 was received from customers out which 53435 was cash sales .the remainder constituted receipts from credit customers. What was the sales revenue for the year?
Sir kindly help me find the answer as i am not able to understand kaplan’s solution