A concentric cylinder viscometer may be formed by rotating the inner member of a pair of closely fitting cylinders. The annular gap is small so that a linear velocity profile will exist in the liquid sample. Consider a viscometer with an inner cylinder of 4 in. diameter and 8 in. height, and a clearance gap width of .001 in., filled with castor oil at 90 degrees F. Determine the torque required to turn the inner cylinder at 400 rpm.