Write a function called 'return_list' that takes a string as a parameter and returns a list of words in the string. "Words" are entities that are seperated by either commas (',') or spaces (' '). In case the string contains neither commas nor spaces, the string will be returned without any manipulation. Note: We are not testing for the case where both commas and spaces are present in the string so feel free to ignore that.

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)?