please answer "identify any schedule M-1 adjustments" question

Part 2. Shelby, Inc. (a calendar year taxpayer) provides you with the following summary of its allowance for doubtful accounts for 2020: ALLOWANCE FOR DOUBTFUL ACCOUNTS Balance on 1/1/20 175,000 A/R Writeoffs : Collections on A/R 2/20 5,500 Previously Written Off: 4/20 8,250 5/20 (Written off: 7/19) 2,200 5/20 2,175 7/20 (Written off: 5/17) 6,700 6/20 9, 200 10/20 (Written off: 2/20) 4,000 7/20 5,425 9/20 11,950 Year End Adjustment: 11/20 1,350 12/31/20 55,950 Balance on 12/31/20 200,000 What is Shelby's 2020 bad debt expense for tax purposes? Identify any Schedule M-1 adjustments that will appear in Shelby's 2020 Form 1120