The following data were taken from the Oxon Hill, Inc. balance sheet:

Accounts payable	$1,150
Inventory	1,250
Retained earnings	40
Accumulated depreciation	300
Cash	15,500
Serial bonds payable ($1,200 matures each year)	10,800
Prepaid insurance	1,200
Allowance for doubtful accounts	720
Capital stock	440
Property, plant, and equipment	1,000
Accounts receivable (gross)	3,110
Accrued salaries	1,310

Required: Compute working capital.