(a) If property is disposed of in a manner that conditions the right of a beneficiary to succeed to an interest in the property on the beneficiary surviving another person, the beneficiary is considered not to have survived the other person unless the beneficiary survives the person by 120 hours, except as provided by Subsection (b).
(b) If an interest in property is given alternatively to one of two or more beneficiaries, with the right of each beneficiary to take being dependent on that beneficiary surviving the other beneficiary or beneficiaries, and all of the beneficiaries die within a period of less than 120 hours, the property shall be divided into as many equal portions as there are beneficiaries. The portions shall be distributed respectively to those who would have taken if each beneficiary had survived.