Write the SQL code for the following.

1. list the customer number, first name, last name, and balance for every customer whose balance is greater than average balance.

a. List the total for each order.

b. list the total for those orders over $200.

c. List each credit limit and the number of customers having each credit limit.

d. Repeat exercise c, but list only those credit limits held by more than one customer.

e. For each customer with a $1,000 credit limit whose balance does not exceed the credit limit, increase the credit limit to $1,200.