Duty for preventing harm defined

A person is under a duty for preventing harm to another (a) if he is under a duty, as mentioned in section 100, to supply a person with necessaries of health and life; or (b) if he is otherwise under a duty, by virtue of the provisions of any statute, or by virtue of any office or employment, or by virtue of a lawful order of any court or person or by virtue of any agreement or undertaking, to do any act for the purpose of thereby averting harm from any person, whether ascertained or unascertained.