In an RDBMS, system catalogs typically contains some statistics about the relations and indexes in the database. Which one of the following options is not part of the statistics parameters? a. Index height for each tree index. b. Average primary key values (AvgKeys) for each tree index. c. Number of tuples (NTuples) d. Number of distinct key values (NKeys) and NPages for each index. e. Number of pages (NPages) for each relation.