6. (20 pts.) Consider the following block diagram where the feed forward terms are summations and the feedback terms are differences. R(s) k, s+1 s+3 s+1 P(s) s+1 Y(s) S+4s+4 (a) Find the general Transfer function for the system above. (b) Find the zero-frequency gain if k,=1 and kc=0. (c) If noise, N(s)=1/s, is injected (added) to the right of the plant, P(s) what is the new value of Y(s)?