Lesson 4: The quiet failure mode that catches most savers by surprise.Same $500 a month. Cash vs. investing.Predict the gap.Two people save $500 a month for 40 years. One keeps it in cash, the other invests it. How do they finish?ANeck and neckThey saved the same amount.BThe investor finishes several times ahead.CThe cash saverSafer and richer, with nothing risked.