Answer
$x=10$ cars per minute (between $I_{1}$ and $I_{2}$)
$y=6$ cars per minute (between $I_{1}$ and $I_{3}$)
Work Step by Step
With the solution set found in Ex.31,
$\{(z+6, z+2, z),\ z\in \mathbb{R}\}$,
for z=4,
$(z+6, z+2, z)=(10, 6, 4)$
$x=10$ cars per minute (between $I_{1}$ and $I_{2}$)
$y=6$ cars per minute (between $I_{1}$ and $I_{3}$)
