A falling-head permeability test is being conducted on a saturated sample of clayey silt having hydraulic conductivity of 6.5 x 10-9 m/s. The diameter and the length of the sample are 100 mm and 150 mm, respectively. If a 5 mm diameter standpipe is used and the initial height of water in the standpipe (measured from the datum taken at the base of the soil sample) is 1.0 m, calculate the height of water in the standpipe after 4 hours.