The first project has present values of future cash flows of $520.66; the second of $52.07; the third of

$60.74. The profitability indexes are $520.66/$500 ≈ 1.04, $52.07/$50 ≈ 1.04, and $60.74/$50 ≈ 1.21.

Nevertheless, you should go with the first project, because it has the highest net present value. The discrepancy between the NPV and the profitability rule recommendations is because the latter does not take project scale into account.