On a hillslope with regolith 1.2 m thick, and regolith production rate of 8 m/yr, what is

On a hillslope with regolith 1.2 m thick, and regolith production rate of 8 μm/yr, what is the mean residence time of regolith in the regolith column?

Now you note that this slope is 100 m long and that the regolith is uniform in thickness. Calculate the residence time another way, this time by addressing the entire regolith ‘reservoir’ on the hillslope, and the volumetric regolith discharge rate at the base of the slope. Are the calculated residence times equivalent?