42 The aquifer described in Problem 40 has a gradient of 0.00115, a hydraulic conductivity of 1,000 m/d, and a porosity of 0.23. (a) What is the Darcy velocity? (b) What is the average linear velocity of the groundwater? (c) If the front edge of a plume is perfectly straight, how long would it take to travel to well 1 after first arriving (simultaneously) at wells 2 and 3, assuming a retardation factor of 2? 5.39 Change the aquifer to a "Sand" aquifer (Specific Yield) 5.42 Change the K = 1,400 m/d (Velocity, Plume)