I can't seem to figure out how to make this work. It wants me to create a new method for perimeter, and I've done that. However, when I define radius, it says it is undefined so I remove the radius. Then it says, Oops, try again. Your perimeter method fails on Circle with radius 1 where it returns NaN when it should return 6.283 etc.

```
function Circle (radius) {
this.radius = radius;
this.area = function () {
return Math.PI * this.radius * this.radius;
};
// define a perimeter method here
};
function Circle (perimeter) {
this.perimeter = function () {
return 2 * Math.PI * this.radius;
}
}
```