A CNC milling machine was purchased by Proto Tool and Die 10 years ago for $75,000. The existing machine can be sold now for an unknown amount $X or used for 3 more years at an annual operating cost of $63,000 and a salvage value of $25,000. A challenger will cost $130,000 with an economic life of 6 years and an operating cost of $32,000 per year. Its salvage value will be $45,000. Assume an interest rate of 12% per year. On the basis of these estimates, what market value (i.e. $X) for the existing machine will render the challenger equally attractive? $6, 966 $5, 966 $4, 966 $0