function plot_pke_results(t, X, U, plant, Q_sg, plot_title)
% PLOT_PKE_RESULTS  Standard 4-panel plot of PKE + T/H simulation results.
%
%  Inputs:
%    t          - time vector from ODE solver
%    X          - state matrix (M x 10): [n, C1..C6, T_f, T_c, T_cold]
%    U          - control input trajectory (M x 1): scalar u at each time
%    plant      - parameter struct from pke_params()
%    Q_sg       - function handle Q_sg(t) used in the simulation
%    plot_title - (optional) string used in the figure name and first subplot

    if nargin < 6 || isempty(plot_title)
        plot_title = 'PKE + T/H closed-loop';
    end

    % --- Extract states ---
    n      = X(:, 1);
    T_f    = X(:, 8);
    T_c    = X(:, 9);
    T_cold = X(:, 10);
    T_hot  = 2 * T_c - T_cold;

    % --- Convert temperatures to Fahrenheit for display ---
    CtoF = @(T) T * 9/5 + 32;
    T_f_F    = CtoF(T_f);
    T_c_F    = CtoF(T_c);
    T_cold_F = CtoF(T_cold);
    T_hot_F  = CtoF(T_hot);

    % --- Derived quantities ---
    power_MW = n * plant.P0 / 1e6;
    Q_sg_MW  = arrayfun(Q_sg, t) / 1e6;

    rho_fb  = plant.alpha_f * (T_f - plant.T_f0) + plant.alpha_c * (T_c - plant.T_c0);
    rho_tot = U + rho_fb;

    % --- Plot ---
    figure('Position', [100 50 1000 950], 'Name', plot_title);

    % Power & SG demand
    subplot(4, 1, 1);
    plot(t, power_MW, 'b-', 'LineWidth', 1.5); hold on;
    plot(t, Q_sg_MW,  'r--', 'LineWidth', 1.2);
    xlabel('Time [s]'); ylabel('Power [MW_{th}]');
    legend('Reactor Power', 'Q_{sg}', 'Location', 'east');
    title(sprintf('%s — Power and SG Heat Demand', plot_title));
    grid on;

    % Reactivity: controller u, feedback, total
    subplot(4, 1, 2);
    plot(t, U       / plant.beta, 'k-',  'LineWidth', 1.5); hold on;
    plot(t, rho_fb  / plant.beta, 'b-.', 'LineWidth', 1.2);
    plot(t, rho_tot / plant.beta, 'm:',  'LineWidth', 1.5);
    xlabel('Time [s]'); ylabel('\rho [$]');
    legend('u (controller)', 'Feedback', 'Total', 'Location', 'east');
    title('Reactivity');
    grid on;

    % Coolant temperatures
    subplot(4, 1, 3);
    plot(t, T_hot_F,  'r-',  'LineWidth', 1.5); hold on;
    plot(t, T_c_F,    'm--', 'LineWidth', 1.2);
    plot(t, T_cold_F, 'b-',  'LineWidth', 1.5);
    xlabel('Time [s]'); ylabel('Temperature [F]');
    legend('T_{hot}', 'T_{avg}', 'T_{cold}', 'Location', 'east');
    title('Coolant Temperatures');
    grid on;

    % Fuel temperature
    subplot(4, 1, 4);
    plot(t, T_f_F, 'Color', [0.85 0.33 0.1], 'LineWidth', 1.5);
    xlabel('Time [s]'); ylabel('Temperature [F]');
    title('Fuel Temperature');
    grid on;

end