Problem:

d) in this Skärmavbild 2012-10-08 kl. 15.16.41.png

Attempt:

I know how to set price if they pay for a ride, but not how to do it if you give a fixed price. Maybe it's something like $\displaystyle \pi = P_{dayticket} \cdot Q_{daytickets} - 50 - Q_{rides}$

Calculations:

2012-10-08 15.16.29.jpg and 2012-10-08 15.16.37.jpg