A company has a credit balance of $$840$ in its allowance for doubtful accounts. The amount of credit sales for the period is $$112,000,$ and the balance in accounts receivable is $$21,000.$ Assume that the expected credit losses are estimated to be $9\%$ of accounts receivable.

a$.$ What is $(1)$ bad debt expense for the year and $(2)$ the ending balance in the allowance for doubtful accounts?

$1.$Bad debt expenseAnswer $1$

$2.$Allowance for doubtful accountsAnswer $2$

b$.$ How would the answer to part a change $($if at all$)$ if the company had a debit balance of $$840$ in its allowance for doubtful accounts before any adjustment?