At the beginning of the year, X Ltd. had a credit balance of $ 20000 in its allowance for doubtful accounts. During the year X. Ltd. had wrote off $ 12000 of accounts receivable and had recoveries of $ 1500. At the end of the year, using the aging method, X Ltd. determined that a balance of $ 50000 was required in its allowance for doubtful accounts. What was X. Ltd.'s bad debt expense for the year?