private double GetRentalCost(string vehicleTypeName, string regNo, double numberOfDays, double numberOfKm, IRentalService rentalService)
        {
            //
            // Make a rental request and check that registred
            //
            const double currentMilage = 10001;
            var rentalDay = new DateTime(2015, 10, 14);
            var rentalReceipt = MakeRentalRequest(vehicleTypeName, regNo, rentalDay, "19800101-8211", currentMilage, rentalService);
            Assert.IsTrue(rentalReceipt.Status == ERentalRequestStatus.Ok);
            var rentalInfo = rentalService.GetRental(rentalReceipt.RentalNumber);
            Assert.IsTrue(rentalInfo.Status == RentalInfo.ERentStatus.Rented);

            //
            // Make a rental return and check that registred
            //
            var returnReceipt = MakeRentalReturn(rentalReceipt.RentalNumber, currentMilage + numberOfKm, rentalDay.AddDays(numberOfDays), rentalService);
            Assert.IsTrue(returnReceipt.Status == ERentalReturnStatus.Ok);
            rentalInfo = rentalService.GetRental(rentalReceipt.RentalNumber);
            Assert.IsTrue(rentalInfo.Status == RentalInfo.ERentStatus.Returned);

            var rentalToPay = rentalService.GetPriceForRental(rentalReceipt.RentalNumber, _dailyBaseCost, _milageKmBaseCost);

            return rentalToPay;
        }