503. Requisites of valid combination.

The inventive step necessary to make a combination patentable may exist in all or any of the stages of invention1; and a patentable combination may be one producing a new result, or arriving at an old result in a better or cheaper way2, or giving a useful choice of means3. Different considerations apply to each of these cases in order to arrive at a conclusion whether there is an inventive step in the particular combination. The fact that the result is new is itself cogent evidence of invention4; but, if the result is old, it is probably correct to