Certain banks offer its customers a new investment product, which is known as AEX-sparen. A minimal amount of 5000 Euro is put into a bank account and this will be returned after four months plus interest. The interest is the same as the AEX-Index has earned in the previous four months, but is maximized to 10 %. If the AEX-Index has gone down after four months, the initial investment of 5000 Euro will be returned, so the customer is protected against the risk of losing money and has a potential of earning a higher percentage after four months than the (annualized) risk-free rate of 2.5%. It is impossible to predict the stock market with certainty and investments always involve risk. The bank will make advantage of this by guaranteeing the initial investment and still offering a chance to make a nice profit. But who will actually profit more from this, the bank or the customer?