Show that a finite measure on a class is (i) subtractive. i.c. A, ei= 1.2. A, A, and 4, A, e implies 4,-4)(A)-4,), and (ii) monotone. ie., (4) S4) with 4, as in (i). In view of (i), if there is one set in of with finite measure, the proviso (2)-0 is automatically satisfied.