The magnitude of the resultant force is given by the centripetal force, since the car is under a circular motion. So, we have:
[tex]F_c=ma_c[/tex]
The centripetal acceleration is given by:
[tex]a_c=\frac{v^2}{r}[/tex]
Where v is the linear speed and r the radius of the circular motion. Replacing this and solving:
[tex]F=m\frac{v^2}{r}\\F=80kg\frac{(44.3\frac{m}{s})^2}{200m}\\F=785N*\frac{1kN}{1000N}\\F=0.785kN[/tex]