please provide detail explainations.

C20 3. Richards Company's accounting system uses a relational database management system. The system includes a customer master file. If a customer has not made a purchase in over 18 months, the customer's record is moved from the active customer master file to the inactive master file. Below are the tables for the customer master files. Active Customer Master File Customer Code Customer Name Address Other Data Current Balance Baynes San Francisco 2.500 C50 Nash London 3,000 C60 Geoffrey London 3,200 Inactive Customer Master File Customer Code Customer Name Address Other Data De Joria New York Sangster London Wyatt Milan 3,000 a. Suppose that next week you are going to be in London, England, and want to call on all your company's customers, whether active or inactive, who are located there. What two database operations would you perform on the two tables to produce one table with the names of the customers who are located in London? C10 C30 C40 Current Balance 0 0