I thought that the solution posted in the Bonus 3 for problem 4 is slightly wrong in explaining why System II is Stable.
Its given that $ x(t) \le B $
$ y(t) = x(t) * h(t) = \int_{-\infty}^{\infty} x(t)h(t)\, dt $
$ \Rightarrow ~y(t) \le \int_{-\infty}^{\infty} Bh(t)\, dt $
$ \Rightarrow ~y(t) \le B\int_{-\infty}^{\infty} e^t[u(t-2) - u(t-5)]\, dt $
$ \Rightarrow ~y(t) \le B\int_{2}^{5} e^t\, dt $
