Who cares about Domain Rules?

namespace BusinessRules.Evolution_One
{
    /// <summary>
    /// Investor Domain object specific to Australia
    /// </summary>
    public class AustralianInvestor : IInvestor
    {
        #region Fields

        private double income;
        private double taxRate;

        #endregion

        #region C'tors

        /// <summary>
        /// Initializes a new instance of the <see cref="AustralianInvestor"/> class.
        /// </summary>
        /// <param name="income">The income.</param>
        public AustralianInvestor(double income)
        {
            this.income = income;
        }

        #endregion

        #region Properties

        /// <summary>
        /// Gets or sets the income.
        /// </summary>
        /// <value>The income.</value>
        public double Income
        {
            get { return income; }
            set { income = value; }
        }

        /// <summary>
        /// Gets the tax liability.
        /// </summary>
        /// <value>The tax liability.</value>
        public double TaxLiability
        {
            get
            {
                double taxLiability = 0.0;
                double inv_income = Income;

                if (inv_income >= 6001.00 && inv_income <= 25000.99)
                {
                    taxLiability += (inv_income - 6000.99) * 0.15;
                }
                if (inv_income > 25000.99)
                {
                    taxLiability += (25000.99 - 6001.00) * 0.15;
                }
                if (inv_income > 75000.99)
                {
                    taxLiability += (75000.99 - 25001.00) * 0.30;
                }
                if (inv_income >= 25001.00 && inv_income <= 75000.99)
                {
                    taxLiability += (inv_income - 25001.00) * 0.30;
                }
                if (inv_income > 150000.99)
                {
                    taxLiability += (150000.99 - 75001.00) * 0.40;
                }
                if (inv_income >= 75001.00 && inv_income <= 150000.99)
                {
                    taxLiability += (inv_income - 75001.00) * 0.40;
                }
                if (inv_income > 150000.99)
                {
                    taxLiability += (inv_income - 150000.99) * 0.45;
                }
                return taxLiability;
            }
        }

        /// <summary>
        /// Gets the tax rate.
        /// </summary>
        /// <value>The tax rate.</value>
        public double TaxRate
        {
            get
            {
                double inv_income = Income;
                if (inv_income >= 0.0 && inv_income <= 6000.99)
                    taxRate = 0.0;
                else if (inv_income >= 6001.00 && inv_income <= 25000.99)
                    taxRate = 0.15;
                else if (inv_income >= 25001.00 && inv_income <= 75000.99)
                    taxRate = 0.30;
                else if (inv_income >= 75001.00 && inv_income <= 150000.99)
                    taxRate = 0.40;
                else
                    taxRate = 0.45;

                return taxRate;
            }
        }

        #endregion
    }
}