Here is the code:

```
var Circle = function( radius )
{
var _radius = radius,
_area = function()
{
return Math.PI * _radius * _radius;
},
_perimeter = function()
{
return 2 * Math.PI * _radius;
};
this.radius = _radius;
this.area = "Area" + _area();
this.perimeter = "Perimeter" + _perimeter();
this.setRadius = function( radius ) {
_radius = radius;
};
};
```

However I cannot get the this.setRadius() function to successfully mutate the private properties. For instance, I run this:

```
var circle = new Circle(5);
alert(circle.area);
circle.setRadius(10);
alert(circle.radius);
```

And it outputs 78.blah which is correct, then it outputs a radius of 5.

Any suggestions would be greatly appreciated! I thought that since the _area property is a function, it would recalculate each time, but I guess it's not? but why is this.radius not returning the new radius when it is obviously being reset?

Thanks!