a. Plot the response \(x\) by using the step and initial commands, showing the step response, the initial response and the total response in one figure. Verify the steady-state value of \(x\).

b. Plot the response \(x\) by using the lsim command.

\(u(t)\) denotes the unit step.
\(\ddot{x}+\dot{x}+4 x=3 u(t), x(0)=0, \dot{x}(0)=1\)