You give a salesperson $20 for a purchase and recieve change. use your funcktion to find the amount of change from a $4.50 purchase

Adolphin is swimming with her friend. the dolphin jumps to a height of 4.54.54, point, 5 meters above the surface of the water as her friend swims 9.89.89, point, 8 meters directly below her. what is the position of the dolphin's friend relative to the surface of the water? meters