The NPV is 3, but I don't know what formula to use to get to that answer.

d) (10 points) If instead, the investment outflow of x0=1 per customer yielded a perpetual revenue stream such that each payment grows at a constant geometric rate over time so that the perpetual cash flow stream looks like x=(x1,x2,x3,x4,)=(2,3,4.5,6.75,), compute the net present value (per customer) of investing in this technique at a discount rate of 100%