(a) The act, omission, or failure of any official, agent, or other person acting for any individual, association, partnership, corporation, or trust within the scope of his employment or office shall be deemed the act, omission, or failure of such individual, association, partnership, corporation, or trust, as well as of such official, agent, or other person.

(b) Every person who directly or indirectly controls another person liable under any provision of this chapter, every partner, officer, or director of such other person, every person occupying a similar status or performing similar functions, and every employee of such other person who materially aids in the violation is also liable jointly and severally with and to the same extent as such other person, unless the person who is also liable by virtue of this subsection sustains the burden of proof that he did not know, and in the exercise of reasonable care could not have known, of the existence of the facts by reason of which the liability is alleged to exist.