This is my code so far I am lost as how to incorporate the 4

This is my code so far, I am lost as how to incorporate the [4] amplifier into the code?

k=4;
num_1=[1]; den_1=[1 1]; sys_1=tf(num_1,den_1);
num_2=[1 0]; den_2=[1 0 4]; sys_2=tf(num_2,den_2);
num_3=[2 2]; den_3=[1 2 1]; sys_3=tf(num_3,den_3);
num_4=[1 0 2]; den_4=[1 0 0 14]; sys_4=tf(num_4,den_4);

sys_g=series(sys_1,sys_2);

sys_fb1=feedback(sys_g,sys_3);

sys_fb2=feedback(sys_fb1,sys_4);

Solution

Modified Matlab Code:

k=4;
num_1=1; den_1=[1 1]; sys_1=tf(num_1,den_1);
num_2=[1 0]; den_2=[1 0 4]; sys_2=tf(num_2,den_2);
num_3=[2 2]; den_3=[1 2 1]; sys_3=tf(num_3,den_3);
num_4=[1 0 2]; den_4=[1 0 0 14]; sys_4=tf(num_4,den_4);
sys_g=series(sys_1,sys_2);
sys_fb1=feedback(sys_g,sys_3);
sys_fb2=feedback(sys_fb1,sys_4);
sys_5 = tf(4,1);%gain 4
total_sys = series(sys_5,sys_fb2);%total system is in series with gain 4 block

Output:

>> total_sys

Transfer function:
4 s^6 + 8 s^5 + 4 s^4 + 56 s^3 + 112 s^2 + 56 s
----------------------------------------------------------------------
s^8 + 3 s^7 + 7 s^6 + 30 s^5 + 58 s^4 + 105 s^3 + 214 s^2 + 198 s + 56

>> sys_fb2

Transfer function:
s^6 + 2 s^5 + s^4 + 14 s^3 + 28 s^2 + 14 s
----------------------------------------------------------------------
s^8 + 3 s^7 + 7 s^6 + 30 s^5 + 58 s^4 + 105 s^3 + 214 s^2 + 198 s + 56