/**
* Compute amount accrued on a principal using compound interest.
* The interest rate is annual.
* $startDate must be less than or equal to $endDate.
*
* @param double $principal
* @param double $annualRate
* @param date $startDate
* @param date $endDate
* @return double amount
*/
public function amountDue($principal, $annualRate, $startDate, $endDate)
{
$months = Defaults::countMonths($startDate, $endDate);
return round($principal * pow(1 + $annualRate / 100, $months / 12), 3);
}
