4. (6 marks) Here is some data about Ivan Khatchatourian, one of the instructors for this course, at two different times in his life 20 inches At birth Now Height 69 inches Weight under 9 pounds over 180 pounds Fully justify your answers to the questions below, using facts and theorems from the course. Note: Ivan has had a quiet and simple life and nothing sudden or unexpected has happened in terms of his height or weight (a) Show that at least once during his life, Ivan's weight was 50 pounds. (b) Show that at least once during his life, Ivan's height in inches equalled his weight in pounds