A PID controller is used in a system. The error is suddenly changed by 5 in (i.e. a step change in error is introduced) and the following data are obtained. Actual gain ( Kc ) is known as 8. Find the last pressure (as Psig) in 80 th second.

\begin{tabular}{|c|c|} \hline Time, sec & Psig \\ \hline 0 & 10 \\ \hline 20 & 7 \\ \hline 60 & 5 \\ \hline 90 & 3.5 \\ \hline \end{tabular}