$1\mathrm{.}2)$ For a causal LTI system with an input signal $x(t)=e^{-2t}u(t),$ the output signal is $y(t)=3^{-3t}u(t)-3^{-4t}u(t),$

a$)$ Determine the impulse response $h(t)$ of the system. $(6)$

b$)$ Based on the impulse response $h(t),$ determine if the system is causal and stable? Justify