{}
is
Element
of
S
by
PROB_1:4
;
then
consider
A
being
Element
of
S
such that
A1
:
A
=
{}
;
take
A
;
:: thesis:
M
.
A
=
0.
thus
M
.
A
=
0.
by
A1
,
VALUED_0:def 19
;
:: thesis:
verum