What is the term used to describe a file that data is read from?

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)?

In the context of the box model, what is the difference between a margin and a padding? a. a padding lies outside a box border, while a margin lies inside it. b. a padding lies inside a box border, while a margin lies outside it. c. a padding can be adjusted independently, while a margin depends on the size of its box. d. a padding depends on the size of its box, while a margin can be adjusted independently.

What are the 4 basic items that are traded throughout the world?