a proportional-only controller is applied to a stable first-order process with a time constant of 10 minutes. the p controller produces a steady state offset of 0.25 in response to a unit step change in the set-point. to eliminate the offset, it is suggested that a pi controller (with the same proportional gain) be used instead. what is the smallest value of the integral time constant that would guarantee a non-oscillatory closed-loop response under the pi controller?