I am new in AngularJs. I have three Select boxes with ng-options. It was working fine before adding filter.

```
<td style="33%">
    <select ng-options="car.BaseStation for car in UnUsedCars | orderBy:'BaseStation'" ng-model="selected.BaseStation">
        <option value="">All Locations</option>
    </select>
</td>
<td style="33%">
    <select ng-options="car.CarType for car in UnUsedCars | filter: selected.BaseStation | orderBy:'CarType'" ng-model="selected.CarType">
        <option value="">All Car Types</option>
    </select>
</td>
<td style="33%">
    <select ng-options="car.Color for car in UnUsedCars | filter: selected.BaseStation | filter: selected.CarType | orderBy:'Color'" ng-model="selected.Color">
        <option value="">All Car Colors</option>
    </select>
</td>

```

The second Select box is expected to act according to the first select box value and third one is expected to work according to the first and second.

The data to these 3 select came from an array of objects 'UnUsedCars'.
A sample input is as follows:

```
[{
    "CarType" : "Audi",
    "Color" : "White",
    "BaseStation" : "Canada"
},
{
    "CarType" : "BMW",
    "Color" : "White",
    "BaseStation" : "U.S.A"
},
{
    "CarType" : "Benz",
    "Color" : "Black",
    "BaseStation" : "Canada"
}]

```

My JS is as follows

```
       scope.selected = {
            BaseStation: null,
            CarType: null,
            Color: null
        };

        scope.$watch('selected.BaseStation', function() {
            scope.selected.CarType = null;
        });

        scope.$watch('selected.BaseStation', 'selected.CarType', function() {
            scope.selected.Color = null;
        });

```

What are the mistakes I made here?