3. Consider a horizontal hollow tube with a diameter of 20 mm filled with water. The water flowing through the tube (in the + z-direction) experiences a pressure drop of 2 mmHg over a length of 50 mm. Any effects from gravity are negligible. (A) Derive an expression for the axial velocity profile as a function of its radial position uz(r). (B) Determine the volumetric flow rate of water in the tube under these conditions (i.e., give an actual value)? (C)Assume the outer wall of the cylinder can move in the negative-z direction. Determine the velocity that would create a net flow rate of 0. (Ans: C = 66.7 m/s)