Choosing a proportion model

In each situation, state whether the first quantity is directly proportional to the second, inversely proportional to the second, or neither. Give a reason.

1. The total cost of identical concert tickets and the number of tickets bought.
2. The time taken to drive \(120\) km and the average speed of the car.
3. A plumber’s charge, which is \(\$40\) for each visit plus \(\$30\) per hour, and the number of hours worked on one visit.