for question 2 :
clear all
clcDelta_I = ultidyn('Delta_I', [1 1]);
Delta_I = ultidyn('Delta_I', [1 1]);
G = tf(1,[0.1 1])
G1 = G*tf(1,[.05 1])
G2 = G*tf([-.01 1],[.01 1])
G3 = G*tf(4,[1 2 4])
G4 = G*tf(100,[1 2 100])
array = stack(1,G1,G2,G3,G4);
Garray = frd(array,logspace(-1,3,60))...