This is a challenging and most rewarding puzzle to solve, although it makes you put in the time to earn the solution. It exists in two parts that have independent solutions, requires data from a prior page in the book, and the ability to watch a YouTube video in order to get the final answer, which is a ultimately a common 5-letter word. Below are some graded hints leading to the solution. It assumes you know key 76. If you don’t know it, then don’t continue. . .