The depth, h (in mm), of the water runoff down a slope during steady rain 3 , is a function of the distance, x (in meters), from the top of the slope, h=f(x)=0.07x²/³.
a) Explain how you can use your answer to part (b) to estimate the difference in runoff depths between a point 30 meters down the slope and a point 6 meters farther down.