Solution:
head change = dh ~ 119-106 = 13 m --> 13m*3.28ft/m = 42.6 ft
distance = dl = 20*5280 = 105600 ft
v = ki/ne = k(dh/dl)/ne = 150*(42.6/105600)/0.3 = 0.202 ft/d
v = x/t --> t = x/v
t = 105600/0.202 = 523,538 days = 1434 yrs