Mother loaned my brother money before she passed away. He and his wife signed a promissory note stating that the loan would be paid in increments of $100 per week until the loan was paid in full. The note further stated that this loan would be payable to mother's trust estate after she died. Mother died in October, 2007. Brother and his wife have breached the loan terms by not making payments since a month before her death. How may my sister and I, who were also trustees of mother's estate, enforce the promissory note or collect on the debt that my brother and his wife owes?