4. A falling head test was performed on the setup shown below. The water reservoir connected to the top of the soil has a diameter of 6cm and the elevation is maintained at 3cm above the sample (see Figure 1). The water reservoir connected to the bottom of the soil has a diameter of 2cm. The soil sample has a diameter of 6cm, a length of 55cm, and a saturated unit weight of 20kN/m^3. When the test started, the difference in elevationbetween the two reservoirs was 80cm; 25 minutes later, the difference in elevation decreased to 50cm. Each porous stone is 1cm thick. a) What is the hydraulic conductivity of the soil in cm/s? b) What is the difference in elevation between both reservoirs 40 minutes after the test started? c) If the same specimen is subjected to a constant head test under a head difference (difference in elevation between the two reservoirs) of 60cm, how much water will you collect in 20 min? Would you use constant head test for this soil? Diagram ad the start of test 80cm zcm diameter ung. diameter H20 3cm Porous stone Icm 55cm Soil Icm 2.5cm