Landholder was land-rich by inheritance but money-poor, having suffered severe losses on bad investments, but still owned several thousand acres of unencumbered timberland. He had a large family, and his normal, fixed personal expenses were high. Pressed for cash, he advertised a proposed sale of standing timber on a choice 2,000-acre tract. The only response was an offer by Logger, the owner of a large, integrated construction enterprise, after inspection of the advertised tract. Assume the following facts. Logger offered to buy, sever, and remove the standing timber from the advertised tract at a cash price 70% lower than the regionally prevailing price for comparable timber rights. Landholder, by then in desperate financial straits and knowing little about timber values, signed and delivered to Logger a letter accepting the offer. If, before Logger commences performance, Landholder's investment fortunes suddenly improve and he wishes to get out of the timber deal with Logger, which of the following legal concepts affords his best prospect of effective cancellation? 
Bad faith. Equitable estoppel. Unconscionability. Duress.