Which of these could be described by an algorithm as part of a computer program and would also allow a computer to automate the process? Choose all that apply.

A. a process that is never performed the same way twice

B. a highly repetitive process

C. a process with easily defined steps

D. a process that requires a judgment at key points

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)?