$3.$ Consider a causal LTI system with the input$-$output relationship: $()+5()+4()=().$ A particular input is observed $()=2()22().($a$)$ Find the frequency response $()$ of the LTI system. $(5$ points$)($b$)$ Find $(),$ the Fourier transform of the input $().(4$ points$)($c$)$ Determine the output signal $().(6$ points$)($d$)$ Find the impulse response $()$ of the LTI system. $(5$ points$)($e$)$ Is this system stable? Use $|()|$ $$ $.$