W.J. King: “Promises, schedules, and estimates are necessary and important instruments in a well-ordered business…You must make promises ... No one should be allowed to avoid the issue by the old formula, “I can’t give a promise because it depends upon so many uncertain factors.”

William Swanson: ”Promises, schedules, and estimates are important instruments in a well-ordered business… You must make promises. Don't lean on the often-used phrase, "I can't estimate it because it depends upon many uncertain factors."