Which of the following is NOT true: A magnetic wheel that spins rapidly, generating electric signals that are converted to sound: A) is part of the Hammond organ.
B) is in instruments played by Booker T. Jones.
C) is called a tone wheel.
D) employs bellows and wind systems to make music.

In a file-oriented information system, a transaction file stores relatively permanent data about an entity is created and saved for backup and recovery purposes stores records that contain day-to-day business and operational data is a temporary file created by an information system for a single task

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?

Description: write function lastfirst() that takes one argument—a list of strings of the format "lastname, firstname" —and returns a list consisting of two lists: (a) a list of all the last names (b) a list of all the first names