Hi can someone please advise what i did wrong on below youll see marked X . pleaseeee help!

Estimating Doubtful Accounts Performance Bike Co. is a wholesaler of motorcycle supplies. An aging of the company's accounts receivable on December 31 and a historical analysis of the percentage of uncollectible accounts in each age category are as follows: Estimate what the proper balance of the allowance for doubtful accounts should be as of December 31. Performance Bike Co. Estimation of Uncollectible Accounts December 31 Age Interval Balance Estimated Uncollectible Accounts Percent Estimated Uncollectible Accounts Amount Not past due $520,000 3/4% $ 39,000,000 X 1-30 days past due 57,200 2 11,440 X 31-60 days past due 26,000 9 23,400 X 61-90 days past due 18,700 14 2,618 91-180 days past due 13,500 40 5,400 Over 180 days past due 9,900 65 6,435 Total $645,300 439,293