An office chair manufacturer models its weekly production since 2001 by the function N(t) = 100 + 25t, where t is the time, in years, since 2001, and N is the number of chairs. The size of the manufacturer's workforce can be modelled by the function W(N) = 3N. a) Write the size of the workforce as a function of time. b) State the domain and range of the function in part a) that is relevant to this problem. Sketch its graph. An environmental scientist measures the pollutant in a lake. The concentration, C(P), in parts per million (ppm), of pollutant can be modelled as a function of the population, P, of the lakeside city, by C(P) = 1.28P + 53.12. The city's population, in ten thousands, can be modelled by the function P(t) = 12.5 x 220, where t is the time, in years. a) Determine an equation for the concentration of pollutant as a function of time. b) Sketch a graph of this function. c) How long will it take for the concentration to reach 100 ppm?