When writing a query, write the query in a way that it would work over all possible database instances and not just for the given example instance!

Give an expression in the relational algebra to express each of the following queries:

A. List the names of all customers who spent more than every customer on product Product A :

B. Fine name the categories of all products with price greater than $100.

C. Find all products located in every category of Electronics.

D. Find the product with the highest total sales amount.

Consider the following Employer database schema and example instance: Customers Orders OrderDetails Products