instructions.md

In this exercise you'll be working with savings accounts. Each year, the balance of a savings account is updated based on the interest rate. The interest rate the bank gives depends on the amount of money in the accounts (its balance):

• -3.213% for a negative balance.
• 0.5% for a positive balance less than 1000 dollars.
• 1.621% for a positive balance greater or equal than 1000 dollars and less than 5000 dollars.
• 2.475% for a positive balance greater or equal than 5000 dollars.

You have three tasks, each of which will deal the balance and its interest rate.

1. Calculate the interest rate

Implement the SavingsAccount.interest_rate method to calculate the interest rate based on the specified balance:

SavingsAccount.interest_rate(200.75)
#=> 0.5

Note that the value returned is an instance of Float.

2. Calculate the annual balance update

Implement the SavingsAccount.annual_balance_update method to calculate the annual balance update, taking into account the interest rate:

SavingsAccount.annual_balance_update(200.75)
#=> 201.75375

Note that the value returned is an instance of Float.

3. Calculate the years before reaching the desired balance

Implement the SavingsAccount.years_before_desired_balance method to calculate the minimum number of years required to reach the desired balance:

SavingsAccount.years_before_desired_balance(200.75, 214.88)
#=> 14

Note that the value returned is an instance of Integer.