Bank.Account.CalculateInterest C# (CSharp) Method

        public abstract decimal CalculateInterest(int monthsCount);

        public double TotalInterestPaid()
        {
            double totalInterest = 0;

            for (int i = 0; i < accounts.Count; i++)
            {
                Account a = (Account)accounts[i];
                if (a.CalculateInterest() > 0)
                {
                    totalInterest += a.CalculateInterest();
                }
            }
            return(totalInterest);
        }