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