december 31 2017 2016 cash $ 33,500 $13,000 accounts receivable 12,250 10,000 inventory 12,000 9,000 availableforsale debt investments 0 3,000 buildings 0 29,750 equipment 45,000 20,000 patents 5,000 6,250 $107,750 $91,000 allowance for doubtful accounts $ 3,000 $ 4,500 accumulated depreciationequipment 2,000 4,500 accumulated depreciationbuilding 0 6,000 accounts payable 5,000 3,000 dividends payable 0 5,000 notes payable, shortterm (nontrade) 3,000 4,000 longterm notes payable 31,000 25,000 co