pls help me Here is a graph of the tide heights for a town in Delaware over a full day. For the graphed situation, describe the dependent and independent variable. How does the dependent variable change? Be specific as possible

Every weekday, mr. jones bikes from his home to his job. sometimes he rides along two roads, the long route that is shown by the solid lines. other times, he takes the shortcut shown by the dashed line. how many fewer kilometers does mr. jones bike when he takes the shortcut instead of the long route?