inline class functions from different classes, both inline?

this may be a dumb question but im curious

when you define a function in a class in c++ it is automatically inlined.

what happens when you have 2 classes and class 'a' calls a function from class 'b', both functions having being defined in respective header files, are they both expanded as inline?

class a
{
   void check_stuff()
   {
      b.do_stuff(param);
   }
};

class b
{
  type xyz;

  public:
  void do_stuff(type in)
  {
     xyz += in; 
  }
};