n = 4;
x = [0.3 0.4 0.5 0.6];
fx = [0.5488 0.4493 0.3679 0.3012];
q = 0;
sum = 0;
for i = 1:n
  p = 1;
  for j = 1:n
    if i ~= j
      p = p*(0.47-x(j))/x(i)-x(j);
    end
  end
  q = p*fx(i);
  sum = sum+q;
end
sum
exp(-2*sum)