18. To compute the distribution of a volatile solute between a hydrocarbon polymer phase(e.! polybutane) and the vapor phase, a weight fraction activity coefficient(n) is used. The activity of the solute in the liquid phase is: asolute = Wsolute(Ohm) where Wsolute is the weight fraction of the solute in the polymer The weight fraction activity coefficient has the advantage of being nearly constant over a wide range of temperatures and nearly linear in weight fractions below 0.1. What is the reason for using a weight fraction activity coefficient for solutes in a polymer? A. the vapor pressure of polymers is very low b. The viscosity of concentrated polymer solutions is high c. the density of the polymer is different from the density of the solute d. The molecular weight of a polymer is an undefinable value, unlike the solute