Biểu đồ 1 1 Online Book sales of Amazon stayed the same at 2 5 million from January to February 2 Online Book sales of Amazon increased rapidly from 2 5 million to 3 5 million between February and March 3 There was a dramatic rise in Online Book sales of Amazon from 3 5 million to 4 5 miliion from March to April 4 There was a sudden drop in Online Book sales of Amazon from 4 5 million to 1 5 million between April and May 5 Online Book sales of Amazon rose quickly again from 1 5 million to 3 mill.