The following mistakes can render a contract unenforceable for failure of mutual assent: a mistake by one party as to the subject matter of the contract a mutual mistake as to the value of the ring that was being sold a mistake by both parties on which diamond ring was being sold under the contract a mistake by one party on the how the item being sold will be shipped to the person. If the offeree [person the offer was made too] changes the terms of the offer in her acceptance, under common law contracts, it is a(n): valid acceptance if not rejected within 48 hours a rejection of the offer and counter-offer an invitation to engage in further discussion and negotiations a clear indication that they lack the capacity to enter into a contract Select the answer that best describes the contract according to the categories we discussed in class: Harold writes to Jeff, "I will give you $600 for your car." Jeff sends back a letter that says, "I accept." bilateral; express; executory; valid. unilateral; implied; executory; valid bilateral; express; executed, valid unilateral; express; executory; void. The Wildlife and Fishing Bureau sets a strict legal limit on the maximum amount of fish a commercial fisherman may catch each day. Ocean Inc., a seafood distributor, agrees to buy for "cash" from Pai, a commercial fisherman, all of the fish that he catches in excess of the legal limit. This agreement is most likely enforceable. valid. void. voidable. A valid offer must be: written, seriously intended and communicated to the offeree definite, voluntarily made and conveyed in a non-threatening manner seriously intended, clear and definite and communicated to the offeree