Neco 2022 Data Processing Question 45

A file contains 10 000 records, each 100 bytes long. The disk has a block size of 4 096 bytes, an average rotational latency of 5 ms, a seek time of 3 ms, and a transfer rate of 80 MB/s. Consider three file‑organization methods: 1. **Sequential**: records are stored consecutively; to access a random record the system seeks to the start of the file and then reads sequentially until the record is found. 2. **Indexed**: a primary index with one entry per block (key and block address) fits in a single block. To locate a record the system reads the index block, then seeks to the appropriate data block. 3. **Direct (hashed)**: a hash function maps a record key directly to a block; assume no collisions. Assuming a uniform random distribution of record positions, calculate the average time (in milliseconds, rounded to two decimal places) required to retrieve a randomly selected record for each method.