Water drains at a constant rate through a saturated soil column with a diameter of 1 ft and a height of 2.5 ft. The hydraulic head is maintained at 4.7 ft at the top of the column and 1.4 ft at the bottom. After a period of 1 hr, 0.06 ft3 of water has drained through the column. What is most nearly the hydraulic conductivity (ft/s) of the soil? a. 9.1 times 10^-6 ft/s
b. 4.6 times 10^6 ft/s
c. 3.5 times 10^-6 ft/s
d. 7.1 times 10^-6 ft/s