Control of HIV/AIDS: The linearized HIV infection model has the following transfer function: P(s) = Y(s) U1(s) = 520s 10.3844 s3 2.6817s2 0.11s 0.0126 It is desired to develop a policy for drug delivery to maintain the virus count at prescribed levels. For the purpose of obtaining an appropriate u1 (t), a feedback will be used as shown below: As a first approach, consider G(s)=K, where K is a constant to be selected. (a) Use the Routh-Hurwitz criterion to find the range of K for which the closed-loop system is stable. (b) Following the MATLAB file ch6p2.m, write a MATLAB code to obtain this range using MATLAB. (c) Select a value of K for which the system is marginally stable and plot the unit step response for t=0 till t=10,000s. (d) Select a value of K for which the system is stable and plot the unit step response for t=0 till t=10,000s. (e) Select a value of K for which the system is unstable and plot the unit step response for t=0 till t=10,000s