Question 4 Consider the following relation and query: B(bid, accNo), accNo is a key. A(accNo, code, balance), accNo is a key. Select B.bid, Sum(A.balance) From B, A Where B.accNo=A.accNo Group by B.bid This query computes the sum of the balances at each branch. Assume that there a clustered B+ tree index on B.bid and a hash index on A.acc No. Discuss the plans of evaluating the query with lowest 1/0 cost. If A and B have |A| and |B| pages, and each page has 100 records, what is the 170 cost? (Hint: use index to reduce the cost of join and sorting cost for aggregation). Explain steps and show you work. Providing just the calculation with no explanation is not suffice. Question 4 Consider the following relation and query: B(bid, accNo), accNo is a key. A(accNo, code, balance), accNo is a key. Select B.bid, Sum(A.balance) From B, A Where B.accNo=A.accNo Group by B.bid This query computes the sum of the balances at each branch. Assume that there a clustered B+ tree index on B.bid and a hash index on A.acc No. Discuss the plans of evaluating the query with lowest 1/0 cost. If A and B have |A| and |B| pages, and each page has 100 records, what is the 170 cost? (Hint: use index to reduce the cost of join and sorting cost for aggregation). Explain steps and show you work. Providing just the calculation with no explanation is not suffice