Assignemnt #103 and Keychains for sale 3

Code
/// Name: Yordan Rashkov
/// Period: 7
/// Program Name: Keychains for sale 3
/// File Name: KFS3.java
/// Date Finished: 3/29/2016

import java.util.Scanner;

    public class KFS3
    {
        public static void main(String[] args)
        {
            Scanner k = new Scanner(System.in);
            int opt;
            int numOfKeys = 0;
            int priceForKey = 10;
            double taxrate = .0825;
            int Shipping = 5;
            int perKeychainShipping = 1;
    
            System.out.println("Ye Olde Keychain Shoppe");
    
            do
            {
                System.out.println();
                System.out.println("1. Add Keychains to Order");
                System.out.println("2. Remove Keychains from Order");
                System.out.println("3. View Current Order");
                System.out.println("4. Checkout");
                System.out.println();
                System.out.print("Please enter your choice: ");
                opt = k.nextInt();
    
                System.out.println();
    
                if (opt == 1)
                {
                    numOfKeys = addKeychains( numOfKeys );
                    System.out.println("You now have " + numOfKeys + " keychains.");
                }
                else if (opt == 2)
                {
                    numOfKeys = removeKeychains( numOfKeys );
                    System.out.println("You now have " + numOfKeys + " keychains.");
                }
                else if (opt == 3)
                    viewOrder( numOfKeys, priceForKey, taxrate, Shipping, perKeychainShipping );
                else if (opt == 4)
                    checkout( numOfKeys, priceForKey, taxrate, Shipping, perKeychainShipping );
                else
                    System.out.println("ERROR");
            } while (opt != 4);
        }
    
        public static int addKeychains(int numOfKeys)
        {
            Scanner k = new Scanner(System.in);
            int keyNum;
            int add;
    
            do
            {
                System.out.print("You have " + numOfKeys + " keychains. How many to add? ");
                add = k.nextInt();
                
                if ( add < 0 )
                    System.out.println("Sorry, but you cannot ask for a negative number of keychains.");
            } while ( add < 0 );
            
            keyNum = numOfKeys + add;
            
            return keyNum;
        }
    
        public static int removeKeychains(int numOfKeys)
        {
            Scanner k = new Scanner(System.in);
            int keyNum;
            int remove;
    
            do
            {
                System.out.print("You have " + numOfKeys + " keychains. How many to remove? ");
                remove = k.nextInt();
    
                if ( numOfKeys < remove )
                    System.out.println("Sorry, but you cannot remove that many keychains.");
                if ( remove < 0 )
                    System.out.println("You cannot remove a negative number of keychains.");
            } while ( numberOfKeys < remove || remove < 0 );
            
            keyNum = numOfKeys - remove;
    
            return keyNum;
        }
    
        public static void viewOrder( int numOfKeys, int priceForKey, double taxrate, int Shipping, int perKeychainShipping )
        {
            double totalCost;
    
            System.out.println("You have " + numOfKeys + " keychains.");
            System.out.println("Keychains cost $" + pricePerKey + " each.");
            System.out.println("Shipping charge is $" + Shipping + " plus $" + perKeychainShipping + " per keychain.");
            
            totalCost = (numOfKeys * priceForKey) + (numOfKeys * perKeychainShipping) + Shipping;
            
            System.out.println("Your subtotal before tax is $" + totalCost + ".");
            System.out.println("The tax on your order is " + (taxrate * 100) + "%.");
            
            totalCost = (totalCost * taxrate) + totalCost;
    
            System.out.println("Your final cost is $" + totalCost + ".");
        }
    
        public static void checkout( int numOfKeys, int priceForKey, double taxrate, int Shipping, int perKeychainShipping )
        {
            Scanner k = new Scanner(System.in);
    
            System.out.println("CHECKOUT");
            System.out.println();
    
            System.out.print("What is your name? ");
            String name = k.next();
    
            viewOrder( numOfKeys, priceForKey, taxrate, Shipping, perKeychainShipping );
            
            System.out.println("Thanks for your order, " + name + "!");
        }
    
    }