Whats the difference between search engine and web browser?

Im doing this last minute and literally none of my neighbors or people that my dad works with use excel so if anyone could me make up an example

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)?

In microsoft word, when you highlight existing text you want to replace, you're in              a.  advanced mode.    b.  automatic mode.    c.  basic mode.    d.  typeover mode