$1.$ Derive an equation for the constitutive relation between total stress sigma and total strain u for a

three$-$element viscoelastic material defined by a dashpot $($viscosity mu$\_(0))$ in series with a Voigt element

$($with viscosity mu and modulus G$).$

$2.$ Primary tendon bundles from tail tendons of young male mice were subjected to creep with a

constant stress of $50$ kPa $.$ The following data are obtained. A Voigt model is employed to describe the

viscoelastic property of the specimen and the modulus G has been obtained from relaxation as

$5\mathrm{.}24$ xx$10^(5)$Pa$.$ Find the viscosity with the best accuracy possible using the given data below.