MyStack. push(new Integer(8)); myStack. push(new Integer(6)); Integer num1 = myStack. pop(); myStack. push(new Integer(3)); myStack. push(new Integer(4)); myStack. push(new Integer(15)); myStack. push(new Integer(12)); myStack. push(new Integer(9)); myStack. pop(); myStack. pop(); myStack. pop(); myStack. push(new Integer(19)); The resulting stack (from bottom to top) is:

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)?