Toyota is considering the purchase of a new robotics machine for assembling the car's engine. This investment requires an initial outlay of $240,000 (at year 0) and will generate net cash savings of $31,000 per year for 15 years. The machine also requires some maintenance at the end of year 10, which costs $60,000. At the end of year 15, the machine can be sold for a salvage value of $25,000. The annual discount rate is 15%. a) What is net present value (NPV) of this investment? b) What is the profitability index (PI)? c) What is the internal rate of return (IRR)? d) What is the modified internal rate of return (MIRR)