/// <summary> /// invoke calculate tax method within the taxCalculator class. assign returned value into Inherited TotalTaxAmount property. /// </summary> /// <param name="payee"></param> public override void CalculateTax(Payee payee) { var taxCalculator = new TaxCalculator(); //create new instance of Type TaxCalculator. TotalTaxAmount = Math.Round(taxCalculator.CalculateTax(payee), 2); //rounding the result into 2 decimal places. }