The number of book sold

The number of book sold was fairly steady over the first few weeks of the year with a slight rise to 200 per day (A). After that sales went up and down wildly, first doubling to 40o units, and subsequently falling back erratically again to 200 books (B). These fluctuations were followed by a period of stability as sales hovered around the 200 marks (E). Book purchases, however, proved very erratic again, but the trend was upward this time, reaching the 400 per day level (F). The number of books sold then plunged dramatically, hitting a low of 100, only to bounce back to 500 books a day (I). The recovery was short-lived, however, as sales fell back again to 200 around which they remained for a short time before climbing again albeit fitfully to 400 (D). Book sales then plummeted to a new low of 50 a day where they stabilized for a period before shooting up again to the 600 mark (G). This was followed by a sharp drop of approximately 80% in the number of books purchased (J).