The rate at which a machine operator's efficiency, $E(t)$ (expressed as a percentage), changes with respect to time $t$ is given by $$\frac{dE}{dt}=8-4 t$$ where $t$ is the number of hours the operator has been at work.

(A) Find $E(t)$, given that the operator's efficiency after working 2 hours is $80\%$ that is, $E(2)=80$.

Operator's efficiency function $E(t)=$

(B) What is the operator's efficiency after $8$ hours?