Suppose that v is a signed measure on and
Proof so far.
a) Now , so we have
Since , we have , P and N are disjoint, and N is -null, P is -null.
If I pick , then I will have .
And that proves (a). (b) should be similar I think.
But I'm a bit lost on (c), mainly because of the sums there.
If I rewrite , will it help?