PLM Inc. is evaluating two machines. Both machines meet the firm's quality standard. Machine X costs $40 000 initially and $1000 per year to maintain. Machine Y costs $24 000 initially and $2000 per year to maintain. Machine X has a six-year useful life and Machine Y has a three-year useful life. Both machines have zero salvage value. Assume the firm will continue to replace worn-out machines with similar machines and that the discount rate is 25%. Which machine should the firm purchase? Select one: a. The firm is indifferent to the two machines. O b. There is not enough information to answer the question. c. Machine X O d. Machine Y