Answer
$125,000$ milliseconds or $125$ seconds
Work Step by Step
To retrieve a record from the middle of the file, you would need to access approximately half of the records. With 50,000 records, accessing the middle record would require accessing the 25,000th record. Since each record takes 5 milliseconds to interrogate, the total time to retrieve the record from the middle of the file would be:
25,000 records * 5 milliseconds/record = 125,000 milliseconds
So, you should expect to wait 125,000 milliseconds or 125 seconds.
