public override double CalculateInterestAmount(int number_of_months) { if (Customer.GetType().Name == "CompaniesCustomer") { if (number_of_months <= InterestMonthsCompanies) { return((this.InterestRate * number_of_months) / 2); } } if (Customer.GetType().Name == "IndividualCustomer") { if (number_of_months <= InterestMonthsIndividuals) { throw new ArgumentException(NoInterestIndividual); } } return(this.InterestRate * number_of_months); }