If you design a three$-$layer asphalt pavement using the AASHTO method, what are

the appropriate thicknesses of each layer $($asphalt $($D$1)$ base $($D$2)$ and subbase $($D$3))$

that meet the following design conditions?

Design conditions

Design Period $=20$ years

Expected ESALs $=18\mathrm{.}6{10}^6$

Reliability $=95\%$

So $=0\mathrm{.}35$

$\frac{}{P}SI=2\mathrm{.}1$

Subgrade Modulus $=5700$ psi

Subbase Modulus $=11000$ psi

Subbase Coefficient $($a$3)=0\mathrm{.}08$

Subbase Drainage Coefficient $(m3)=1\mathrm{.}2$

Granular Base Modulus $=30000$ psi

Granular Base Coefficient $($a$2)=0\mathrm{.}14$

Granular Base Drainage Coefficient $($m$2)=1\mathrm{.}2$

AC layer Modulus $=400000$ psi

AC layer coefficient $(a1)=0\mathrm{.}4.$

$D1=5in$;$D2=6\mathrm{.}6in$; and D$3=7in$

$D1=6\mathrm{.}6in$;$D2=5\mathrm{.}9in$; and D$3=5\mathrm{.}0in$

D$1=8in$;$D2=7in$; and D$3=12$ in

$D1=7in$;$D2=8in$; and $D3=10$ in