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([1,5],[2,9]);line([2,9],[3,2]);line([3,2],[4,1]);line([4,1],[5,6]);line([5,6],[6,4]);line([6,4],[7,8]);text([4,-1],"Day of Week","below");]

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