Pros and cons of being a computer engineer

The forerunner to cell phones, pdas, and smartphones was

Why is investing in a mutual fund less risky than investing in a particular company's stock? a. mutual funds only invest in blue-chip stocks. b. investments in mutual funds are more liquid. c. mutual funds hold a diversified portfolio of stocks. d. investments in mutual funds offer a higher rate of return.

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)?