Calculate the Area of a Circle

lic double CalculateArea(double radius)
{
    return Math.PI * radius * radius;
}

public double CalculateVolume(double radius)
{
    return Math.PI * Math.Pow(radius, 3);
}

public double CalculateMass(double radius)
{
    return CalculateVolume(radius) / CalculateDensity(radius);
}

public double Calculate