4. It is desired to tests the system's response to a step input voltage of 10 V (the maximum voltage for this particular DC motor). Given that? m = 1000 N-m/A, ?= 0.001 V-s/rad, R = 10, ? = 0.9 N-m/(rad/s), and ?= 0.1 kg-m, plot the step response using MATLAB functions tf() and step(). Comment on the validity of our system model given the results. If any assumptions were broken, suggest a simple modification to the mechanical system such that the assumption is satisfied with the same input voltage. Plot the modified system's step response.