Using isothermal stress relaxation data at various temperatures, shift factors have been measured for a nolyurethane material as shown in the table below: (a)(20) Plot log behavior?aT Vs. 1/T (•K);

compute an average activation energy based on Arrhenius aT vs. T( C) and compare with WLF equation with Tg =-35 C.(b) (20)Plot log(Note that Tref=0.)