(15\%) A S-mm-diamater glass tube was immersed in a liquid bath composed of oil, water and mercury layerby-layer (see the figure). The thickness of oil layer and water layer was 1mm and 2mm, respectively. The contact angle between mercury and glass, , was 135. All the components were at 20C. Please solve for the "th" in the figure. [Hint] Analyze the force on the free mereury body in the tube. The weight of the free mercury body is neglected Densities at 200C Oil: 950kg/m3 Water 1,000kg/m3 Mercury: 13,580kg/m3 Surface tension, , Mercury in air at 20C:0.44N/m \$(12\%) A tank initially contains 200kg of brine containing 5% salt by mass. An inlet stream of brine containing 20% salt by mass flows into the tank at a rate of 20kg/min. The mixture in the tank is kept uniform by stiming. Brine is removed from the tank via an outlet pipe at a rate of 10kg/min. Find the amount of salt in the tank at any time r. (need to solve for the I" ODE)