You completed the wireframe step of mobile app development. Which statement is true about this step? In this step, you defined your target audience and main goal.
You have drawn pictures of what your screens will look like and identified the input-process-output that occurs on each screen.
Your app is functioning and ready to test.
This step involved comparing your app to other apps already available

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)?