Having trouble understanding the NPV Formula please help

You are planning to invest $15,000 in research \& development (R\&D). This investment will generate cost savings of $10,500 in year 1 and $7,500 in year 2 . After 2 years, the salvage value is zero. The cost of capital is 25% a year. a) Compute the net present value. NPV =$ b) Following a government stimulus program, the cost of capital decreased to 10% a year. Compute the net present value at the new cost of capital NPV=$ Should you invest now? OYES ONO c) The economy is at full employment and is beginning to overheat (i.e., total demand exceeds the available capacity, which leads to rapid increases The Federal Reserve can control the cost of capital in the economy by adjusting its benchmark interest rate. To reduce the investment activity, the Federal Reserne should: reduce the interest rate based on (a) and (b), lower cost of capital will reduce investment