function Jg = Jacg(c,t)
% this function is used in a minimization problem
  for i = 1:length(t)
      Jg(i,:) = [ 1 exp(c(3)*t(i))  t(i)*c(2)*exp(c(3)*t(i))  exp(c(5)*t(i))  t(i)*c(4)*exp(c(5)*t(i))];
  end
end