$9\mathrm{.}7$ How much difference would there be in the $($a$)$ computed ultimate settlement and $($b$)$ the time required for $90\%$ consolidation for the soil conditions of Example $9\mathrm{.}7$ if the clay layer were doubly drained?

Example $9\mathrm{.}7$

Given:

A $10m$ thick clay layer with single drainage settles $9cm$ in $3\mathrm{.}5yr.$ The coefficient of consolidation for this clay was found to be $0\mathrm{.}544{10}^{-2}c\frac{m^2}{s}.$