Answer :
The cart slows that at the rate of 20cm/s between 5 and 15secs
Given the rate function expressed as:
r(t) = 2t + 60
If the time is t = 5
r(5) = 2(5) + 60
r(5) = 70cm/s
If the time is t = 15
r(15) = 2(15) + 60
r(15) = 90cm/s
Taking the difference in rate;
Difference = 90cm.s - 70cm/s
Difference = 20cm/s
Hence the cart slows that at the rate of 20cm/s between 5 and 15secs
Learn more on rate of functions here:
https://brainly.com/question/13516577