The line graph below shows the number of times Maria drove her car each day of the week.

[Graphs generated by this script: initPicture(-1,8,-2,10);axes(1,1,1,1,1);marker="dot";line([1,2],[2,9]);line([2,9],[3,7]);line([3,7],[4,5]);line([4,5],[5,4]);line([5,4],[6,8]);line([6,8],[7,6]);text([4,-1],"Day of Week","below");]

How many times did Maria drive her car on day 4?