The figures show simulaitons of responses to step changes in F1 and in F4. The attached code is for the seocnd simulaiton: step in F4 (problem 2C). To simulate the step in F1 (problem 2A), adjust the lines in the functions Flow1() and Flow4(), to get the step in F1 and to remove the step from F4. Adjust the plot title to say "F1" or "F4".
I realize this is not your assignment, because you are doing this symbolically. This shows a numerical solution. See my comments separately about the "steady state" heights, which are not really steady state.