Interest Calculation on Savings Account

I am trying to find interest on a savings account for the following transactions in an mvc.net application:

Date          Balance
-----------   -------
01-Apr-2011    100
05-Apr-2011    200
30-Apr-2011    300
28-Jun-2011    400

The interest rate is 4% per annum.

Is there a simple way to calculate simple interest for these transactions for the quarter (i.e. 01-Apr-2011 - 31-Jun-2011)? Once I figure it out the calculation for one account, I will write a function to calculate it for 开发者_C百科all accounts. I got the Average Daily Available Balance(ADAB) as 24500 / 91 = $269.23. I used the below formula to get the simple interest for the quarter. Is it correct? Is there any other method to calculate the interest without using ADAB?

ADAB x (annual interest / 365 x number of days), or 269.23 x (0.04 / 365 x 91) = 2.6849

Sorry, neither calculation is correct. First, 4% interest should be expressed as 0.04. Next, the simple interest calculation should be ADAB x (annual interest / 365 x number of days), or 269.23 x (0.04 / 365 x 91) = 2.6849.

Because this is 4% simple interest for one quarter, if your answer is not roughly 1%, there is a problem.