It is unlawful for a broker-dealer, salesperson, investment adviser, or investment adviser representative knowingly to effect or cause to be effected, with or for a customer's account, transactions of purchase or sale (1) that are excessive in size or frequency in view of the financial resources and character of the account and (2) that are effected because the broker-dealer, salesperson, investment adviser, or investment adviser representative is vested with discretionary power or is able by reason of the customer's trust and confidence to influence the volume and frequency of the trades.