If I were the Stockholm public transit company, I'd get my employees to join Planka, get fined every day, and send the bill to Planka. Let's see how they like being on the receiving end of fraud for a change.
I don't see the point of plotting the derivative on the same graph as the function, and I think this will confuse students who are exposed to the derivative for the first time. Functions and their derivatives have different units, and only rarely do they need to be plotted together.
Once it is understood that the derivative is an expression that gives us the slope of the tangent at any point of the original graph, then it may be interesting to remark that the derivative is in fact a function, and may therefore be plotted, or differentiated, or set equal to zero to find its roots.