=+The set function P* has four properties that will be needed: (i) P*() = 0; (ii) P*

=+The set function P* has four properties that will be needed:

(i) P*(Ø) = 0;

(ii) P* is nonnegative: P*( A) ≥ 0 for every A CO;

(iii) P* is monotone: A C B implies P*(A) ≤ P*(B);

(iv) P* is countably subadditive: P*(U ,, A,) ≤ E„, P*( A ,, ).