Answer
$L=10km$
Work Step by Step
By making a small angle approximation, we obtain $D=L*\theta_R$, where L is the distance to the headlights and D is the separation of the headlights.
Solving for L, we obtain:
$L=D/\theta_R$
Using our answer from part a, $\theta_R=1.34*10^{-4}rad$, we obtain:
$L=1.4m/1.34*10^{-4}rad$
$L=1.0*10^4m$
$L=10km$
