<u>Answer:</u>
The right graph is the first one (figure attached).
Note that in a Speed vs Time graph, the constant speed is represented by a line with slope=0 <u>(for example, segment 1)</u>, when the speed increases the slope is positive <u>(for example, segment 2)</u> and when the speed decreases the slope is negative <u>(for example, segment 4).</u>
Now, if we want to prove this, let’s read again the problem, <u>dividing each section of the path Marc drove to his work</u> (see figure attached):
1. He slowly pulls out of his driveway at a <u>constant speed </u>
2. and then his <u>speed increases</u> steadily
3. until he reaches the speed limit. He uses cruise control to drive the speed limit <u>(he drives at constant speed)</u>
4. until he comes upon some traffic (usually if you find some traffic you have to <u>derease your spped</u>)
5. He then slows down to a new <u>constant speed</u>.
6. When he gets near his office, his <u>speed steadily decreases</u> until he comes to a stop right in front of his office building <u>(at this point the speed is zero)</u>
