No, the function is not one to one function and it has no inverse function.
Because the long distance call costs are step functions, as the call lasting minutes costs sames as the call lasting minutes.
Inverse does not exist.
![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=e7dba78396da02d16b0c79b61f151425.png\")
is not one to one function and it has no inverse function. ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=afbccc0842c90047dc87da192a4d1019.png\")
minutes costs sames as the call lasting ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=96f8703482fece915b66bb78e952908b.png\")
minutes.![\"\"](\"/userfiles/image/steps_images/solution.JPG\")