Juan cannot revoke his offer of $ 500 for this reason because in his ad he did not establish a time limit on finding and returning the necklace.
Juan established an offer for whoever finds his necklace with specific conditions and a retribution value of $ 500. Once a person reads the ad and looks for the necklace and finds it, it can be inferred that he accepted the agreement, so Juan cannot change his offer from $ 500 to $ 300.
If Juan had the intention of lowering the amount of compensation money for whoever found his necklace after a while, he must have expressed this in the advertisement that he published. Therefore, Juan must pay $ 500 for his necklace.
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