E xercise 14.2.1: Suppose that blocks can hold either ten records or 99 keys and 100 pointers. Also assume that the average B-tree node is 70% full; i.e., it will have 69 keys and 70 pointers. We can use B-trees as part of several different structures. For each structure described below, determine (i) the total number of blocks needed for a 1,000,000-record file, and () the average number of disk I/O s to retrieve a record given its search key. You may assume nothing is in memory initially, and the search key is the primary key for the records. a) The data file is a sequential file, sorted on the search key, with 10 records per block. The B-tree is a dense index. b) The same as (a), but the data file consists of records in no particular order, packed 10 to a block.