Is "Gemilus Chasadim", Doing favors for others, (other than lending money), a מצוה חיובית מן התורה - a mandatory Mitzvah of the Torah, or is it a Mitzvah Kiyumis, If one does it he is rewarded, but it is not mandatory?
If one is driving somewhere by car, and he knows of someone else who needs to travel to the same place, is he obligated to offer the other person to join him in his car, (If it would not require any extra expense or time)?
If one is traveling abroad, and someone asked him to take along a package/ piece of luggage for him to the same destination, is he obligated by the Torah to take it if he can?
Even if added time and expense were involved, if it is a Mitzvah Chyuvis then why should one not have to spend money (חומש נכסיו - see Shulchan Aruch/Rema in siman 556), or time on it as with other mitzvos?
[Please address the main question first, whether doing chessed is a mandatory mitzvah, (with or without added time and expense), and not just the specific examples.]