The situation in part (a) requires more work.
There is no work required for part (b) because the distance is .
![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=fcd348ebf66f4047fc23f05f2c058874.png\")
.