What is the difference between a key escrow and a recovery agent? (choose all that apply.)

a. the former is primarily for third party access to data

b. the latter is primarily for third party access to data

c. the former is primarily for internal users

d. the former has replaced the latter in many occasions

e. the latter is primarily for internal users

One subtask in the game is to roll the dice. explain why is roll the dice an abstraction.

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)?

How to do this programming flowchart?