$6\mathrm{.}17$ A new four$-$lane divided multilane highway $($two lanes in each direction$)$ is being planned with $3\mathrm{.}6-m$ lanes, $1\mathrm{.}8-m$ shoulders on both sides, and an $80-k\frac{m}{h}$ speed limit$.$ One $3\%$ downgrade is $7\mathrm{.}2km$ long, and there will be $2\mathrm{.}5$ access points per kilometer. The peak$-$hour directional volume along this grade is estimated to consist of $1800$ passenger cars, $140$ large trucks, $40$ buses, and $10$ recreational vehicles. If the peak$-$hour factor is estimated to be $0\mathrm{.}85$ and the driver population adjustment factor is expected to be $1\mathrm{.}0,$ what level of service will this segment of highway operate under?