In litigation between Prodigal and Mater's estate, which of the following is a correct statement of the parties' rights with respect to the money on deposit with Vault?
Prodigal prevails, because he took Mater's claim to the savings account by a gratuitous but effective and irrevocable assignment from Mater. 
Prodigal prevails, because his failure to reject the gift, even if the assignment was revocable, created an estoppel against Mater and her estate
The estate prevails, because Mater's gift to Prodigal was revocable and was terminated by her death. 
The estate prevails, because Mater's gift to Prodigal was revocable and was terminated by her express revocation. 