What is the text structure in the text below: (description, cause and effect, problem and solution, sequence/chronological, or compare and contrast) "In many schools, traditional textbooks are being replaced by tablet computers that hold e-copies of all materials necessary for all classes. So far, the effect of this change has been positive. Students no longer have to carry heavy books back and forth from home or between classes. And, as long as they have their tablets, they always have all of the materials needed to complete an assignment. Finally, it is much easier to update e-books, and adding new information is very inexpensive."