Fluid Mechanics - Incompressible, Viscous Fluid Placed Between Horizontal, Infinite, Parallel Plates

Problem/Example Statement: An incompressible, viscous fluid is placed between horizontal, infinite, parallel plates. Two plates move in opposite directions with constant velocities, U1 and U2. Pressure gradient in the x direction is zero. Only body force is due to the fluid weight. Use the Navier-Stokes equations to derive and expression for the velocity distribution between the plates. Assume laminar flow.