Please answer the question in full, but problem C I do not understand the Trial balance adjusted. How is the starting balance 1000?

E #11 (Stretch problem) A partial adjusted trial balance of Rock Company at January 31, 2011, shows the following. ROCK COMPANY Adjusted Trial Balance 31-Jan-11 Debit Credit Supplies $850 Prepaid Insurance 2,500 Salaries Payable $800 Unearned Revenue 750 Supplies Expense 950 Insurance Expense 500 Salaries Expense 1,700 Service Revenue 2,000 Instructions Answer the following questions, assuming the year begins January 1. (a) If the amount in Supplies Expense is the January 31 adjusting entry, and $1,500 of supplies was purchased in January, what was the balance in Supplies on January 1? (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? (e) If $3,500 of salaries was paid in January, what was the balance in Salaries Payable at December 31, 2010? (d) If $1,650 was received in January for services performed in January, what was the balance in Unearned Revenue at December 31, 2010? Supplies Expense E3-a 300 Supplies 1,500 850 950 950 950 X + 1,500 - 950 = 850 E3-b July 1, 2015 5 2500/500 = 5 months left after Jan 31st, policy ends June 30, thus policy began July 1, prior year [E3-c 2,600 Salaries Expense Salaries Payable 1,000 1,900 1,700 800 1,700 1,700 Note: if Sal Payable has a beginning balance of $1,000, and $1,700 was accrued in January (Debit Salaries Expense, Credit Salaries Payable), and the ending balance is $800, you can calculate the amount paid. (Debit Salaries Payable, Credit Cash): $800 = $1,000 +1,700 - X. Note that some of the $1,700 will be paid in February. E3-d 1,100 Unearned Revenue 1,100 Service Revenue 350 1,650 750 2,000 of Service Revenue has an ending balance of 2,000, with only 1,650 being for the current month's performance, then the rest of the 2,000 must be for unearned revenue which is now earned. 2,000 = 1,650 + X. X=350, so the beginning balance in Unearned Revenue must be 1,100