Recognize Constant Rate Changes Practice Test

A tank is being filled so that the volume increases by 12 liters every 3 minutes. Is the rate of change of volume with respect to time constant? If so, what is the constant rate in liters per minute?

A car travels at a steady speed of 55 miles per hour for $t$ hours.

Is the rate of change of distance with respect to time constant? What type of function models distance vs. time?