7-4B please help answer attached question. thank you!

SUNLAND CORPORATION Analysis of Changes in the Allowance for Doubtful Accounts For the Year Ended December 31, 2017 Balance at January 1, 2017 Provision for doubtful accounts Recovery in 2017 of bad debts written off previously Deduct: write-offs for 2017 (90162+62100) Balance at December 31, 2017, before change in accounting estimate Increase due to change in accounting estimate during 2017 Balance at December 31, 2017, adjusted Computation of Allowance for Doubtful Accounts at December 31, 2017 Aging Category Nov-Dec 2017 July-Oct Jan-June Prior to 1/1/17 135700 90162 20000 152262 245862 152262 245862 245862 93600 178,642 272242 r Doubtful Accounts , 2017 Doubtful Balance % Accounts 1180600 2% 23612 659600 10% 65960 440500 24% 105720 95000 81% 76950 272242