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diff --git a/257/CH11/EX11.21/example_11_21.sce b/257/CH11/EX11.21/example_11_21.sce
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+++ b/257/CH11/EX11.21/example_11_21.sce
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+s=poly(0,'s'); 
+F=syslin('c',[k/((1+0.2*s)*s*(0.05*s+1))])                  //without k
+
+fmin=0.1;                                        //Min freq in Hz
+fmax=20;                                          //Max freq in Hz
+
+scf(1);clf;
+bode(F,fmin,fmax);                                //Plots frequency response of open-loop system in Bode diagram
+
+show_margins(F)                                //display gain and phase margin and associated crossover frequencies
+
+// TO FIND VALUE OF K
+
+k= 10^(26/20)
+disp(k,"k marginal = ")
+
+// for GM=10 dB, the point on the plot without k is 16dB away from 0dB line.
+k1=10^(16/20)                                      // 20*log(k1)=-10
+disp(k1,"k for GM=10 is ")
+
+
+// for PM=40degrees, the point on the magnitude plot without k is 12dB away from 0dB line.
+k2=10^(12/20)                                      // 20*log(k1)= 6 dB
+disp(k2,"for PM=40degrees k is ")