Graph the step function for cost of postage stamp in the U.S from to .
Graph the step function by using the data.
In the graph the years represent the numbers.
Graph:
.
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=e98b9eecc1858af42b3eb76e6b04a97b.png\")
to ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=8b0f45782744c1f8ea1fb543f309eecd.png\")
. to .![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=3a845d2a4fccaaff6b074c2d31c90c30.png\")