11. A system has the transfer function

s+a T(s)= 4 +683 +12s2+12s+61 Determine the values of a that render the system unobservable. a. a=1.30 or a = -1.44 b. a = 3.30 or a = 1.44 c. a=-3.30 or a = -1.44 d. a = -5.7 or a = -2.04