Answer
See the figure below.
Work Step by Step
Given:
$\bullet$ $v_{i}=60\;\rm mi/h$
$\bullet$ $\Delta t_1=30\;\rm s$
$\bullet$ $\Delta t_2=30\;\rm s$
$\bullet$ $v_{f}=30\;\rm mi/h$
Before reaching the city car's speed was constant, 60 mi/h. When it reaches the city, it slows down at a constant rate until it reaches a final speed of 30 mi/h. The author here asks about the motion diagram before reaching the town by 30 seconds and after reaching the town by 30 seconds as well and here it is.
