The intestate share of a decedent's surviving spouse is:
(a) The entire intestate estate if:
(1) No descendant of the decedent survives the decedent; or
(2) All of the decedent's surviving descendants are also descendants of the surviving spouse and there is no other descendant of the surviving spouse who survives the decedent;
(b) Three fifths of the intestate estate, if all of the decedent's surviving descendants are also descendants of the surviving spouse and the surviving spouse has one or more surviving descendants who are not descendants of the decedent;
(c) One half of the intestate estate, if one or more of the decedent's surviving descendants are not descendants of the surviving spouse.