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On 1 July 2017, Montana Lid had an opening balance for accounts receivable of $90,000 DR and an allowance for doubtful debt of $25,000 CR. On 3 October 2017, Montana made $60,000 of credit sales to customers. On 5 December 2017, a customer BHP declared bankruptcy and would not be able to pay the amount of 10,000 owed. On 3 April, 2018, BHP managed to repay 20 cents in the dollar. Montana used the percentage of credit sales method to estimate doubtful debt expense at year end of 2018. Past experience suggests that 2% of credit sales are uncollectible. Starting from 1 July 2018, Montana switched to a percentage of accounts receivable method to estimate bad debt. At 30 June 2019, Montana had accounts receivable of $1,000,000 and doubtful debts were estimated based on 3% of accounts receivable. Since 1 July 2019, Montana started to use an aging analysis of accounts receivable to estimate bad debt. Below is an account receivable aging chart by 30 June 2020. Customer name 0-30 Days 31-60 Days 61-90 Days 90+ Days Holden $40,000 $40,000 Canva $10,000 $90,000 $70,000 CBH Group $40,000 Percentage 1% 3% 10% 20% Required: (a) Prepare an adjusting entry at 30 June 2018 for doubtful debt. Show all workings. (2 marks) (b) Prepare a ledger account for allowance for doubtful debt based on all relevant journal entries from 1 July 2017 to 30 June 2018. Show all workings. (6 marks) (c) Prepare an adjusting entry at 30 June 2019 for doubtful debt. Show all workings. (3 marks) (d) Prepare an adjusting entry at 30 June 2020 for doubtful debt. Show all workings