Question #$3[20$ pts$]$

A flexible pavement has a $4-$inch sand$-$mix asphalt wearing surface, $10-$inch soil cement base, and

a $10$ inch crushed stone subbase. It is designed to withstand $40020-$kip single axle loads and $900$

$35-$kip tandem axle loads per day. The subgrade CBR is $8,$ overall standard deviation is $0\mathrm{.}45,$ initial

PSI is $4\mathrm{.}2$ and the final PSI is $2\mathrm{.}5.$ What is the probability that this pavement will have a PSI above

$2\mathrm{.}5$ after $30$ years? Assume the drainage coefficients are $1\mathrm{.}0.$