function norc = cal_s_core(guess, ys0_, M_)

% set s
M_.params(find_string_index(M_.param_names, {'s'})) = guess;

% get all variables
[~,params_,~] = PH_steadystate_sublevel(ys0_, 0, M_);

% maximising U equivalent to minimising norc

norc = params_(find_string_index(M_.param_names, {'norc'}));

end