Need help with this, explanations to help me understand will also be great! Thanks

In 2019, ABC Co began operations and sold $100 software licenses to 100 customers. Sales were made with 90 day credit terms. ABC estimated that 5 customers will not pay the amount owed and established the appropriate allowance for uncollectible accounts. No balances were written off in 2019. During 2020, ABC decided to stop trying to collect from 6 customers they sold to in 2019 (so they wrote off the receivables). They also sold $100 software licenses to another 125 customers. As of year-end, ABC believes 8 of the customers who they have not yet collected from will not pay the amount owed. Prepare the required adjusting journal entry for uncollectible accounts for the end of 2020