Since a stick note i completely flat (paper) there isn't the 3rd dimension, height. So it cannot be measured with volume, but area. To find the area, multiple the leight by the width, to get the answer.
Answer:
It's the second one. Press 'Ask For Help' if you need more help on problems

Write

, and recall that for a differentiable function

, the derivative at a point

is given by

which would suggest that for this limit,

and

. We have

, and so the value of the limit would be

.
To find the unit rate you would need to find the cost per ounce of potato chips. To find this you would simply divide. $3.80/20 = .19
So the unit rate in your question is $0.19
Hope this helps! :)