Problem: Lexicon McCoy runs a brokerage firm in New York City. He amasses a fortune by paying investors alleged "profits" gleaned solely from money provided by other investors who think that McCoy is actually placing that money into legitimate stocks. For certain clients, McCoy does in fact invest in stocks, but he constantly buys and sells those stocks simply for the purpose of charging his clients a commission. Lexicon also trains a group of ten employees to implement his schemes on a wider scale. When he fears that police may be investigating his operation, he opens an offshore bank account using the social security number of an unsuspecting client. He hides $1,000,000 in that account. By constantly buying and selling his clients' stocks for no reason other than to generate commissions for himself, Lexicon has engaged in: a. churning b. insider trading c. a Ponzi scheme d. structuring