A beneficial owner of more than 10 percent of a class of equity security, or a director or officer, may not, directly or indirectly, sell an equity security of the company if the person selling the security or the principal of that person (1) does not own the security sold, or (2) if owning the security, does not deliver it against the sale within 20 days after the sale or does not within five days after the sale deposit it in the mails or other usual channels of transportation; but a person shall not be considered to have violated this section on proof that notwithstanding the exercise of good faith the person was unable to make the delivery or deposit within the time prescribed, or that to do so would cause undue inconvenience or expense.