I have a question asking for the minimum and maximum height $h$ of a B-Tree with 1000 elements under following conditions:
- each block can save 1 to 4 records,
- the number of internal nodes is between 3 and 5 and
- the root has between 3 and 5 children.
The solution is given as $4\leq h \leq7$. How this is reached?