End-of-period adjustments West Laboratory adjusts and closes its accounts at the end of each month. The trial balance at September 30, 2010, before adjustments is as follows: Cash Medical Fees Receivable Prepaid Rent Office Supplies Medical Equipment Accumulated Depreciation: Medical Equipment Accounts Payable Notes Payable Unearned Medical Fees Capital Stock Retained Earnings Dividends Medical Fees Earned Salaries Expense Utilities Expense Insurance Expense Debit Credit $18,200 27,000 5,000 1,200 21,800 $ 6,000 3,000 8,000 14,000 18,000 16,000 1,000 31,000 14,000 2,000 5,800 $96,000 $96,000 The following information relates to month end adjustments: (a) Office supplies on hand September 30 amounted to $500. (b) The useful life of the medical equipment was estimated to be 20 years with no residual value. (c) Many patients pay in advance for major medical procedures. Fees of $6,000 were earned during the month by performing procedures on patients who had paid in advance. (d) Salaries earned by employees during the month but not yet recorded amounted to $2,300. (e) On September 1 West Laboratory had moved and paid 2 month's rent in advance. (f) Medical procedures performed during the month but not yet billed or recorded amounted to $4,600. Prepare the adjusting entries required at September 30.