Physics I - Old Questions

10.Two horizontal capillary tubes A and B are connected together in series so that a steady stream of liquid flows through them. A is 0.4 mm in internal radius and 250 cm long while B is 0.3 mm in internal radius and 40 cm long. The pressure of the fluid is 7.5 cm of Hg above the atmospheric pressure at the entrance point of A. At the exit point of B the pressure is atmospheric (76 cm of Hg). What is the pressure at the junction of A and B? (4)