clc
clear
s=0;
loopN=1;
N=1000000;
while 1
P=12;
mP=P.*(1+normrnd(0,0.03));
% s=s+normrnd(0,0.03);
s=s+P-mP;
loopN=loopN+1;
if loopN>N
break
end
s=s/N