At year-end, March 31, 2017, Waterton Contractors showed unadjusted balances of $243,000 in Accounts Receivable; $1,100 debit in Allowance for Doubtful Accounts; and $4,640,000 in Sales. Uncollectible ac- counts are estimated to be 0.4% of sales.
Unadjusted balances at March 31, 2018, were Accounts Receivable, $298,000; Allowance for Doubtful Accounts, $900 debit; and Sales, $3,971,000. Waterton changed the method of estimating uncollectible accounts to 5.5% of outstanding accounts receivable.
At March 31, 2019, the general ledger showed unadjusted balances of: $253,000 in Accounts Receiv- able; $4,600 credit in Allowance for Doubtful Accounts; and $3,750,000 in Sales. Waterton prepared an aging analysis on March 31, 2019, that estimated total uncollectible accounts to be $12,900.

Required 

Prepare the 2017, 2018, and 2019 year-end adjusting entries to estimate uncollectible accounts.
Analysis Component: List the adjusted balances in Allowance for Doubtful Accounts for each of March 31, 2017, 2018, and 2019. Beside each, show the respective Accounts Receivable and Sales balances. Comment on the change in Allowance for Doubtful Accounts and Accounts Receivable relative to the change in Sales.