Consider a banking web application that determines the annual interest rate applied to a housing loan (only) based on the tenure (number of years to repay the loan). The annual interest rate is calculated as follows:
• The tenure can be 1 to 20 years.
• If the tenure is between 1 and 5 years, then the rate is 11%.
• If the tenure is between 6 and 10 years, then the rate is 10%.
• If the tenure is between 11 and 15 years, then the rate is 9%.
• If the tenure is between 16 and 20 years, then the rate is 8.5%
What is the minimum number of test cases to be prepared for testing the application using the equivalence class partitioning technique?