Ember extend component by two other components

Assuming we have 3 components. A, B, and C. How to extend component A with functionality from component B and C?

Component A:

import Ember from 'ember';
import B from 'b/components/component';
import C from 'c/components/component';

export default B.extend(C, {});

Above example doesn't work because C is not a mixin. B and C come from npm (Ember CLI addons), so I can't change them.