How to calculate bad debt expense and beginning allowance for doubtful accounts for each year?

Year Total Sales Credit Sales Ending Accounts Receivable Ending Allowance for Doubtful Accounts $25,600 Write-offs of Uncollectible Accounts 2018 $1,250,000 $1,100,000 $256,000 $0 2019 $1,894,000 $1,612,000 $338,520 $33,852 $25,300 2020 $2,477,000 $2,386,000 $501,060 $50,106 $34,700 2021 $3,202,000 $2,870,000 $588,350 $58,835 $50,678 2022 $3,351,000 $3,000,000 $597,000 $59,700 $50,350