JQuery :: Handling If Radio Buttons Are Selected

I'm a just wondering about something that might be quite simple but I'm not sure how to achieve it.

<form>

That's the code for my form. Two radio boxes one called car and one called bus. I'm not so much bothered about the contents of what is selected, just that if car or bus (or both) is selected.

I have two buttons:

If I choose a car such as Ford, I want the car one to be changed to

I also want the submit button to be 'greyed out' until both of them have been submitted which looks like this.