Two layers of fluid are dragged along by the motion of an upper plate as shown in the figure (without mixing). The bottom plate is stationary. The top fluid generates a shear stress on the upper...

Two layers of fluid are dragged along by the motion of an upper plate as shown in the figure (without mixing). The bottom plate is stationary. The top fluid generates a shear stress on the upper plate, and the lower fluid generates a shear stress on the bottom plate. Calculate the velocity of the boundary between the two fluids.