composition analyzer is used to measure the concentration of a pollutant in a wastewater stream. The relationship between the measured composition Cm and the actual composition C is given by the following transfer function (in deviation variable form): 

where θ = 2 min and τ = 4 min. The nominal value of the pollutant is C̅ = 5 ppm. A warning light on the analyzer turns on whenever the measured concentration exceeds 25 ppm. Suppose that at time t = 0, the actual concentration begins to drift higher, C(t) = 5 + 2t, where C has units of ppm and t has units of minutes. At what time will the warning light turn on?

C(8) C'(s) e-Os ts + 1