A battery-manufacturing plant has been ordered to cease discharging acidic waste liquids containing mercury into the city sewer system. As a result, the firm must now adjust the pH and remove the mercury from its waste liquids. Three firms have provided quotations on the necessary equipment. An analysis of the quotations provided the following table of costs.

Bidder1: Foxhill Instrument: Installed Cost: 35,000; Annual Operating Cost: 8,000; Annual Income from Mercury Recovery: 2000; Salvage Value: 20,000

Bidder2: Quicksliver: Installed Cost: 40,000; Annual Operating Cost: 7,000; Annual Income from Mercury Recovery: 2200

Salvage Value: 0

Bidder3: Almaden: Installed Cost: 100,000; Annual Operating Cost: 2000; Annual Income from Mercury Recovery: 3500

Salvage Value: 0

If the installation can be expected to last 20 years and money is worth 7%., which equipment should be purchased?