Here is the question and answer for a B+ database tree insertion, I'm trying to understand how exactly the number of read/write is established and when they happen...thank you

Root 50 73 85 8 1832 40 1256810 41 45 73 80 91 99 Figure 10.1 Tree for Exercise 10.1 2. Show the B+ tree that would result from inserting a data entry with key 3 into the original tree. How many page reads and page writes does the insertion require? Root 1850 73 85 32 39 13 80 9199* Figure 10.3 2. The data entry with key 3 goes on the first leaf page F. Since F can accommodate at most four data entries (d 2), F splits. The lowest data entry of the new leaf is given up to the ancestor which also splits. The result can be seen in figure 10.3 The insertion will require 5 page writes, 4 page reads and allocation of 2 new pages