javascript - Selecting a default value for dependant dropdowns in AngularJS

I need to pre select default values for two dependent dropdowns. So on page load the dropdowns should show something like "Automative" with "Two wheelers" selected.
(And not using selected attribute , the default values have to be loaded via $scope)
Below is the Plunkr link for the working dropdowns.

http://plnkr.co/edit/3Xrpb4jBziWNZE9JVfts?p=preview

   Select Category




  Select Sub Category