Answer:
January 24, 2017, write-off of Madonna Inc.'s debt
Dr Allowance for doubtful accounts 3,943
Cr Accounts receivable 3,943
Since the allowance for doubtful accounts already included Madonna's account as bad debt expense, no further expense should be reported.
March 4, 2017, reversion of Madonna Inc.'s bad debt write-off
Dr Accounts receivable 3,943
Cr Bad debt expense 3,943
March 4, 2017, Madonna Inc.'s debt is collected
Dr Cash 3,943
Cr Accounts receivable 3,943
Two separate journal entries must be made since first we must reverse the previous write-off, and then we must record the cash collection.