//add the rent for the amount
Money interest = getBackingCalculationSystem().calculateInterest( amount, monthYears, monthDays, monthRate );
rentSummer.plus( interest );
//Build the information object (if expected)
interestDetails.add( new InterestDetails( actualMonthBegin, actualMonthEnd, monthRate, baseForMonth, interest.plus( compoundInterest ), monthDays ) );
//Next month --> now we really need the first day of the month
actualMonthBegin = actualMonthBegin.plusMonths( 1 ).withDayOfMonth( 1 );
}