a $20-$ft$-$thick clay layer, normally

consolidated, is subject to a

stress increase at its surface of

$2500$ psf$.$ if the water table is at

the surface of the clay layer and

the clay has a unit weight of

$122\mathrm{.}4$ pcf$,$ a void ratio of $1\mathrm{.}20$ and

compression index of $0\mathrm{.}62,$ the

total consolidation settlement

occuring under these conditions

is most nearly

a$.1$ ft

b$.2$ ft

c$.4$ ft

d$.6$ ft

e$.8$ ft