Which graph shows a set of ordered pairs that represent a function?
54-3-2-1,1 1 3
-5-4-3-2-1, 1 1 2
3
-54-3-2-1, 1 2 3 4 5
5-4-32-1,
12
4

Study results indicate that the mean length of time people spend on a bus in a city is between 21.2 min and 24.5 min what is the study margin of the error?