Will give brainliest!! Help me on 2nd question also explain what it represents thank you

Answer:
A rate of change is a rate that describes how one quantity changes in relation to another quantity. If x is the independent variable and y is the dependent variable, then Rates of change can be positive or negative. This corresponds to an increase or decrease in the y -value between the two data points. So if you subtract 225 and 350, for example, your rate of change would be 125. So the total cost would represent the context of this situation since it is the y variable.