In a falling head permeability test on a fine sand the sample had a diameter of 86 mm and a length of 162 mm with a stand pipe of 13.7 mm diameter. A stopwatch was started when h was 501 mm and read 17.6 seconds when h was 244 mm; the test was repeated for a drop from 254 mm to 97 mm and the time was 22.4 seconds. Determine the average value of k in m/sec.