I would say that each of these passages contains questions above the 85th percentile and a few questions seem much harder than that. There are also questions that are below the 85th percentile and you can expect that even the hardest passage will often have questions that seem easier than the other questions from that passage. You must take these "easier" questions seriously as well.

Remember that for reading comp there are two components of difficulty: the difficulty of the passage and the difficulty of each question.

So for example, on page 412 you have a passage followed by 8 questions. You would not get 8 questions from a single passage on the test. So what is going on here? Depending on how you are doing on the test the computer will select from these questions and give you 4, 5, or 6 questions and that will impact the difficulty as well.

From this passage on pages 412 and 413 (modernization of telephone exchange) you will find that some of the questions seem more difficult than others. I bet you can tell which is which.

Sorry to not give you a specific number value but that is not how RC works. I would say that these passages are tough enough and that even on my way to a perfect 51 on the verbal section I did not see anything tougher than these.