You are using a proportional control Gc = Kc for a feedback control of a process with Gv = 4/ (2s + 1), Gv = 0.6/ (50s + 1), and Gm = 2/(????s + 1) (time constant in seconds). Determine the range of Kc that the feedback loop can stay stable for ???? = 1 and ???? = 20, respectively. Using the Root Locus approach

a. Using the Routh Array approach.
b. Using the Root Locus approach
c. Using the Frequency Response approach