1) Why should NULLS in a relation be avoided as much as possible? Discuss the problem of spurious tuples and how we may prevent it. 2) Define 1st, 2nd, and 3rd normal forms when only primary keys are considered. 3) What undesirable dependencies are avoided when a relation is in 2NF? 4) What undesirable dependencies are avoided when a relation is in 3NF? 5) List all functional dependencies of the following relation: A B C TUPLE# 10 bl cl 1 10 b2 c2 2 11 b4 cl 3 12 b3 c4 4 13 bl cl 5 14 b3 c4 6 6) Consider the following relation: CAR SALE(Car#, Date_sold, Salesperson#, Commission%, Discount_amt) Assume that a car may be sold by multiple salespeople, and hence {Car#, Salesperson#} is the primary key. Additional dependencies are Date_sold Discount_amt and Salesperson# Commission% Based on the given primary key, is this relation in INF, 2NF, or 3NF? Why or why not? How would you successively normalize it completely?