a). During a test on a polymer which is to have its viscoelastic behavior described by the Voight-Kelvin model the following creep data was obtained when a stress of 2MN/m2 was applied to it. The spring constant is 200MN/m2. Use the above information to determine the relaxation time for the polymer and predict the strain after 1500s at a stress of 4.5MN/m2