Hi Vivianne,
If this problem is to be attacked using the Final Value Theorem, we can proceed either numerically or symbolically. Here's the former.
km = 3.5;
tm = 0.5;
K = 5;
s = tf('s');
Define the plant transfer function
G = km/(tm*s+1);
Closed loop transfer function from R(s) to E(s)
EoverR = feedback(1,G*K,-1)
Before trying to find the steady state output, we need to verify that the system is stable.
pole(EoverR)
The single pole is in the left half plane, so the system is stable and we can proceed
SP = 3; %input value
E(s) in response to R(s) = SP/s
E = EoverR*SP/s
The Final Value Theorem tell us that the steady state value of e(t) is the limit as s ->0 of s*E(s)
s*E
We see that the free s in numeator cancels the free s in the denominator, so the limit is simply evaluating SP*EoverR at s = 0
ess = freqresp(EoverR*SP,0)
You can use a similar procedure for the transfer function from D(s) to E(s).
