Commutative contracts are those in which what is done, given, or promised by one party is considered as an equivalent to or in consideration of what is done, given, or promised by the other. Civ. Code La. 1701 ; Ridings v. Johnson, 128 U. S. 212, 9 Sup. Ct. 72, 32 L. Ed. 401. Independent contracts are those in which the mutual acts or promises have no relation to each other, either as equivalents or as considerations. Civ. Code La. 1702.