%1
R1 = 5;
R2 = 12;
R3 =15;
Rn = 20;
L = 0.08;
Ck = 0.00001;
R = Rn + R1 + R2;
A = [-1/Ck/R -R1/Ck/R; R1/L/R -(Rn+R2)*R1/L/R];
B = [1/Ck/R; (Rn+R2)/L/R];
C = [1 0];
D = 0;
sys = ss(A,B,C,D);
%2
sys1=minreal(tf(sys))
%4,5
A = [0 1; -1.689e5 -2757];
B = [0;1];
C = [0 2703];
D = 0;
sys2 = ss(A,B,C,D);
sys3 = minreal(tf(sys2))

A=[-2757 1; -1.689e5 0];
B = [2703; 0];
C = [1 0];
D = 0;
sys4 = ss(A,B,C,D);
sys5 = minreal(tf(sys2))
%6
zpk(sys5)
%7
step(sys,sys1,sys2), grid