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I am sorry to hear about this situation. If client enters into a contract with A, and then with B, for the same thing, then the client is liable to both parties. Obviously only one party is going to do the job, which means that if A does the job, B can still enforce the contract by suing for breach of contract. The elements of a breach of contract claim are that: (1) a contract existed, (2) the contract was breached, and (3) damages flowed from that breach. A.R. Holland, Inc. v. Wendco Corp., 884 So. 2d 1006, 1008 (Fla. 1st DCA 2004).
The relief sought would simply be the money, not necessarily the contract action (if already done by A).
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