Why is hip hop and rap so popular

When is an original work considered public domain? a. when posted via social media b. when it is posted on the internet c. when a copyright symbol is not included with the piece of work d. when explicit permission is given by the author / owner

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)?

Anetwork security application that prevents access between a private and trusted network and other untrusted networks