Find transfer function from root locus and step response diagram?
The transfer function is 

$$H(s)=\frac{K(s - 4)(s + 5)}{(s + 3)(s + 6)(s + 10)}=\frac{K(s^2 + s - 20)}{s^3 + 19s^2 + 108s + 180}$$
So we need to find $K$. 

The LT of input step is $\frac{3}{s}$. Using the FVT for the step response $g(t)$:

$$\displaystyle\lim_{t\to \infty}g(t)=\displaystyle\lim_{s\to 0}s\cdot \frac{3}{s}\cdot\frac{K(s^2 + s - 20)}{s^3 + 19s^2 + 108s + 180}=-4$$
or
$$\frac{3\cdot K\cdot (-20)}{180}=-4$$
which gives $K=12$.
Then use the following code to plot the step response

K= 12;
sys = tf(K*[1 1 -20],[1 19 108 180]);
step(3*sys)




So there is no feedback.