The price is written above each bar. You buy first and sell in a later year.
Look for the buying year and the selling year that give you the most extra. The cheapest year does not always work, a more expensive year has to come after it.
How much more you have is the selling price minus the buying price.
Example
For parents
What does this exercise practice?
The grain market trains reading a bar chart and comparing values in their order.
Common pitfalls
Price and year are easily mixed up. The price is above the bar, the year below it.
How to practice at home
Note down what a roll costs for a week. On which day was it cheapest?