A partial "adjusted" trial balance of Marine Repair Company at January 31, 2021, shows the following. Marine Repair Company Adjusted Trial Balance (partial) January 31, 2021 Supplies. Prepaid Insurance Salaries and Wages Payable Unearned Revenue. Supplies Expense. Insurance Expense... Salaries and Wages Expense Service Revenue. Debit $ 2,100 Credit 14,850 $1,310 3,350 2,380 1,650 7,630 19,880 Required: Answer the following questions, assuming the accounting year begins January 1st. Very Important: Do Not just provide an answer, you must show your detailed work/calculations. (a) If the amount in Supplies Expense is the January 31 adjusting entry, and $3,750 of supplies was purchased in January, what was the balance in Supplies on January 1st? (b) If the amount in Insurance Expense is the January 31 adjusting entry, and the original insurance premium was for one year, what was the total premium and when was the policy purchased? (c) If $7,080 of salaries was paid in January, what was the balance in Salaries and Wages. Payable at the end of December 31, 2020? (d) If $14,445 was received in January for services performed in January, what was the balance in Unearned Revenue at the end of December 31, 2020?