why is my tax not being calculated correctly? internal class Program { 
    static void Main(string[] args)
        {
            Console.WriteLine("**************** INVOICE PRINTER ****************");
            double cost, discount, tax;
            string customerName, customerType, state; 
            string doAgain = "y";
            do
            {
                try {
                    Console.Write("Please enter the customer's name: ");
                    customerName = Console.ReadLine();
                    Console.Write("Enter the type of customer (either R for retail or C for corporate): ");
                    customerType = Console.ReadLine();
                    Console.Write("Enter the customer's state (IL, IN, or WI): ");
                    state = Console.ReadLine();
                    Console.Write("Enter the amount of the purchase: ");
                    cost = Convert.ToDouble(Console.ReadLine());
                    discount = 0; tax = 0;
                    if (customerType.Equals("R"))
                    {
                        if (cost >= 500) {
                            discount = cost * 0.2;                        
                        }
                        else if (cost >= 250 && cost <500){
                            discount = cost * 0.1;
                        }
                        else
                        {
                            discount = cost * 0;
                        }
                    }
                    else if (customerType.Equals("C")) {
                        if (cost >= 1000)
                        {
                            discount = cost * 0.3;
                        }
                        else if (cost >= 500 && cost < 1000)
                        {
                            discount = cost * 0.2;
                        }
                        else {
                            discount = cost * 0;
                        }
                    }
                    

                    if (state.Equals("IL"))
                    {
                        tax = 0.0875 * cost;
                    }
                    else if (state.Equals("IN")) { 
                        tax = 0.0825 * cost;    
                    }
                    else if (state.Equals("WI"))
                    {
                        tax = 0.085 * cost;
                    }

                    Console.WriteLine("Here is the customer " + customerName + " from " + state);
                    Console.WriteLine("Cost of items purchased: " + "$"+cost);
                    Console.WriteLine("Discount applied " + "$"+discount);
                    Console.WriteLine("Taxes applied: " + "$"+tax);
                    Console.Write("Do you have another employee? ");
                    doAgain = Console.ReadLine().ToLower();
                }
                catch (Exception ex) {
                    Console.WriteLine("Your input is invalid");
                }
            } while (doAgain.Equals("y") || doAgain.Equals("yes"));
            Console.WriteLine("Thank you for using this program");
        }
    }
}