Program:

//Define the class

public class TaxComputer

{

    //Declare the necessary constant variables

    private static double basicRate = 4.0;

    private static double luxuryRate = 10.0;

    //Define the function changeBasicRateTo()

    public static void changeBasicRateTo(double newRate)

    {

/*Assign "newRate" into the variable “basicRate”*/

        basicRate = newRate;

    }

    //Define the function changeLuxuryRateTo()

    public static void changeLuxuryRateTo(double newRate)

    {

/*Assign "newRate" into the variable “luxuryRate”*/

        luxuryRate = newRate;

    }

    //Define the function computeCostBasic()

    public static double computeCostBasic(double price)

    {

        //Calculate the “tax”

        double tax = price * basicRate / 100;

        //Calculate the “price”

        price = price + tax;

        //Return the value

        return roundToNearestPenny(price);

    }

    //Define the function computeCostLuxury()

    public static double computeCostLuxury(double price)

    {

        //Calculate the "tax"

        double tax = price * luxuryRate / 100;

        //Calculate the "price"

        price = price + tax;

        //Return the value

        return roundToNearestPenny(price);

    }

    //Define the function roundToNearestPenny()

private static double roundToNearestPenny(double price)

    {

        //Calculate the "price"

        price = price * 100;

        price = java.lang.Math.round(price);

        //Return the value

        return price/100;

    }

    //Define the main() function

    public static void main(String[] args)

    {

        //Print the statement

        System.out.println("Testing the basic rate computation.");

        //Print the statement

        System.out.println(" Item price no tax:10.00");

        //Print the statement

    System.out.println("cost with 4% tax: "+ TaxComputer.computeCostBasic(10.00));

        //Print the statement

        System.out.println("Testing the basic rate computation.");

        //Call the function changeBasicRateTo()

        TaxComputer.changeBasicRateTo(7.5);

        //Print the statement

        System.out.println(" Item price no tax: 10.00");

        //Print the statement

        System.out.println("cost with 7.5% tax: "+ TaxComputer.computeCostBasic(10.00));

        //Print the statement

        System.out.println("Testing the luxury rate computation.");

        //Print the statement

        System.out.println(" Item price no tax: 2019.25");

        //Print the statement

        System.out.println("cost with 10% tax: "+ TaxComputer.computeCostLuxury(2019.25));

        //Print the statement

        System.out.println("Testing the luxury rate computation.");

        //Call the function changeLuxuryRateTo()

        TaxComputer.changeLuxuryRateTo(20.0);

        //Print the statement

        System.out.println(" Item price no tax: 2019.25");

        //Print the statement

        System.out.println("cost with 20% tax: "+ TaxComputer.computeCostLuxury(2019.25));

        //Print the statement

        System.out.println("Testing the basic rate again, should still be 7.5%.");

        //Print the statement

        System.out.println(" Item price no tax: 210.99");

        //Print the statement

        System.out.println("cost with 7.5% tax: "+ TaxComputer.computeCostBasic(210.99));

    }

}

Output:

Testing the basic rate computation.

 Item price no tax: 10.00

cost with 4% tax: 10.4

Testing the basic rate computation.

 Item price no tax: 10.00

cost with 7.5% tax: 10.75

Testing the luxury rate computation.

 Item price no tax: 2019.25

cost with 10% tax: 2221.18

Testing the luxury rate computation.

 Item price no tax: 2019.25

cost with 20% tax: 2423.1

Testing the basic rate again, should still be 7.5%.

 Item price no tax: 210.99

cost with 7.5% tax: 226.81