Answer:
1.
January 31
Dr. Allowance for uncollectible accounts $1,100
Cr. Account Receivable $1,100
2.
March 9
Dr. Cash $600
Cr. Account Receivable $600
Dr. Account Receivable $600
Cr. Allowance for uncollectible accounts $600
Explanation:
A receivable is written off on January, 31, it reduces the account receivable balance and record this amount in Allowance for uncollectible account to adjust the value in the expense for the period by making adjusting entry later on.
When the amount recovered from the written off receivable the entry reversed by passing through the receivable account to again settle that receivable amount in the Allowance for uncollectible account. It effect will be adjusted in the period end adjusting entries.