2. Circle Class

Write a Circle class that has the following member variables:

• radius: a double
• pi: double initialized with the value 3.14159

The class should have the following member functions:

• Default Constructor: A default constructor that sets radius to 0.0.
• Constructor: Accepts the radius of the circle as an argument.
• setRadius: A mutator function for the radius variable.
• getRadius: An accessor function for the radius variable.
• getArea: Returns the area of the circle, which is calculated as

area = pi * radius * radius

• getDiameter: Returns the diameter of the circle, which is calculated as

diameter = radius * 2

• getCircumference: Returns the circumference of the circle, which is calculated as

circumference = 2 * pi * radius

Write a program that demonstrates the Circle class by asking the user for the circle's radius, creating a Circle object, and then reporting the circle's area, diameter, and circumference.