set p = <*1*>;

now

let u be set ; :: thesis: ( u in {1} implies u in INT )
assume u in {1} ; :: thesis: u in INT
then reconsider u' = u as Element of NAT by TARSKI:def 1;
u' is integer number ;
hence u in INT by INT_1:def 1; :: thesis: verum

end;

then {1} c= INT by TARSKI:def 3;
then rng <*1*> c= INT by FINSEQ_1:56;
then reconsider f = <*1*> as FinSequence of INT by FINSEQ_1:def 4;
take f ; :: thesis: ( not f is empty & f is positive-yielding )

now

let r be real number ; :: thesis: ( r in rng f implies 0 < r )
assume r in rng f ; :: thesis: 0 < r
then r in {1} by FINSEQ_1:56;
hence 0 < r by TARSKI:def 1; :: thesis: verum

end;

hence ( not f is empty & f is positive-yielding ) by PARTFUN3:def 1; :: thesis: verum