You are interested in measuring the fluid velocity in a narrow rectangular open channel carrying petroleum waste between locations in an oil refinery. You know that, because of bottom friction, the velocity varies with depth in the channel. If your technician has time to perform only two velocity measurements, at what depths would you take them to obtain the best estimate of the average velocity? State your recommendation in terms of the percent of total depth d measured from the fluid surface. For example, measuring at the top would be 0%d, whereas at the very bottom would be 100%d.