For each of the situations described, decide which technique for data field design listed below would be most\ appropriate and how it could be applied.

• Code lookup table
• Default value
• Range control
• Referential integrity
• Handling missing data

a. The clients of an investment firm can have any one of four account types with the firm.

b. Entering the date of account opening.

c. The age of clients should be between 18 and 75 years, while the minimum level of education should be graduation.

d. Each new client should have a linked account of an existing client to serve as referral or guarantor for opening an account.

e. Monthly reports of client deposit details contain missing values for area code and gender.