Andrew loves skiing-- he just hates the ski lift. To make matters worse, the ski lift has been acting up today. Andrew is using the GPS on his phone to track the ski lift's progress as it travels up the mountain. It moves at a steady rate of 400 feet per minute until it stops suddenly. Andrew calls his friends to tell them he is stuck. They talk on the phone for 10 minutes until finally the ski lift begins moving again. What is the independent quantity? What is the dependent quantity?