Error in problem description for Problem 39(Share Price Volatility)

In this paragraph, real gain should be 400-100-104 = 196 dounds. Not 96 dounds.

"For example, if initial price of shares was 50 (rather than 20) and it had grown to 52 when Paul sold them, his profit for 200 shares would be only 400 dounds. However, comission would be 100 dounds when buying and 104 when selling, so his real gain is only 96 dounds - more than half money was taken by broker!"