$3-$If the time needed for $50\%$ consolidation of a $2-$in high clay specimen $($double drainage$)$ in the laboratory $=8$min, how many days will it take for a $10-$ ft thick clay layer $($with sand on top, and impervious soil at the bottom$)$ in the field to undergo $90\%$ consolidation under the same pressure increment? What is the value of $C_v?(4$ points$)$

$\backslash$table$[[t90\%,$ field $($days$),C_V($ft $f\frac{t^2}{?}$ day$)],[,]]$