janko wellspring incorporated has a pump with a book value of $28,000 and a four-year remaining life. a new, more efficient pump is available at a cost of $49,000. janko can receive $8,400 for trading in the old pump. the old machine has variable manufacturing costs of $29,000 per year. the new pump will reduce variable costs by $11,300 per year over its four-year life. should the pump be replaced?