Problem $1$: For the stress$-$strain curve shown below, determine:

$1-$ The yield stress,

$2-$ The ultimate stress,

$3-$ The yield strain,

$4-$ The Elastic modulus,

$5-$ The ductility factor,

$6-$ Toughness,

$7-$ Plastic strain upon unloading once reaching a strain of $2{10}^{-3}.$ Assume

that the unloading modulus is the same as the Elastic modulus.