The box plots show the average gas mileage of cars and minivans tested by a certain company.

2 box plots. The number line goes from 14 to 34. For cars, the whiskers range from 21 to 33, and the box ranges from 22 to 29. A line divides the box at 24. For minivans, the whiskers range from 14 to 26, and the box ranges from 18 to 21. A line divides the box at 19.

Which is closest to the difference in the medians of the two sets of data?
4
5
7
8