Answer
$7.01$ ft
Work Step by Step
We have the ratio of $\dfrac{\sin \theta_1 }{\sin \theta_2 }=1.333$
Now, $\dfrac{\sin 70^{\circ} }{\sin \theta_2 }=1.333$
Re-write as: $\theta_2 = \sin^{-1} [ \dfrac{\sin 70^{\circ} }{1.333}]$
This implies that $ \theta_2 \approx 44.83^{\circ}$
Now, $x = 4 \tan \theta_2 =4 \tan 44.83^{\circ} \approx 3.98 $ft
and $y = 4 \tan \theta_1 =4 \tan 70^{\circ} \approx 10.99 $ft
Further, $d = y-x = 10.99 -3.98 =7.01$ ft
