Given:

Customers ( cid, cname, city, discount )

Agents ( aid, aname, city, percent )

Products ( pid, pname, city, quantity, price )

Orders ( ordno, mon, cid, aid, pid, qty, dollars )

Write the given SQL query

a) For each product, find its total quantity of sales in all orders.

b) Find the product(s) that has(have) the highest amount of sales in terms of the dollar amount.

c) Find the customer(s) whose average dollar amount per transaction is the lowest