Chapter 12, Problem 12.5P

Consider the feedback system shown in Figure 12.1 .The closed-loop gain $A_f=-80$ and the open-loop gain $A=-2\times {10}^4$ .(a) Determine the feedback transfer function $\beta .$ (b) The closed-loop gain is not to change by more than 0.01 percent when the open-loop gain changes. What is the maximum allowed change in the open-loop gain?