Consider a database that records information for a simplified debit/credit card environment including the following:

Every customer has a name, address, SSN and a unique customer ID.

There are two types of cards: debit cards and credit cards.

Each debit/credit card account has one holder.

Every credit card is identified by its card number and has an expiration date. The current balance and the limit should also be recorded. Credit cards accumulate charges with merchants. Each charge is identified by the date and time of the charge as well as the primary keys of merchant and credit card.

Every debit card is identified by its card number and has an expiration date. The current available amount of money in the card should be recorded.

Merchants are identified by their IDs. Their addresses are also recorded in the database.

a) Draw the E-R diagram

b) Convert the E-R diagram to a relational database schema