Consider a relation R (A, B, C, D, E) and the following query: select * from R where A = '123' and B = '456'. Suppose relation R has 1000 tuples and have 50 unique values of A with each value appearing in exactly 20 tuples. Furthermore, there are 100 unique values of B in R with each value appearing in exactly 10 tuples. For each of the following scenarios, determine the number of tuples that might be accessed to answer the query. . No index is present on any attribute of R ii. An index is present on attribute A only iii. An index is present on attribute B only iv. A multi-attribute index is present on (A,B)