Example:

An $8\mathrm{.}9kN$ car has $C_D=0\mathrm{.}40,A_f=2\mathrm{.}0m^2,$ and an available tractive effort of $1135N.$ If the car is traveling at an elevation of $)=(1\mathrm{.}0567\frac{kg}{m^3}$ on a paved surface at a speed of $110k\frac{m}{h},$ what is the maximum grade that this car could ascend and still maintain the $110k\frac{m}{h}$ speed?