Afirm is trying to decide which of two machines to install to reduce excessive costs of repairs due less reliable old machines. the new machines cost $1000 and have useful lives of five years, and no salvage value. machine a can be expected to result in $300 savings annually. machine b will provide cost savings of $400 the first year, but will decline $50 annually, making the second-year savings $350, the third year savings $300, and so forth. with interest at 7%, which machine should be purchased based on benefit-cost ratio?