$*3-20.$ The stress$-$strain diagram for a bone is shown and can be described by the equation $=0\mathrm{.}45(10^-6)\backslash$sigma $+0\mathrm{.}36(10^-12)\backslash$sigma $^3,$ where $\backslash$sigma is in kPa. Determine the modulus of toughness and the amount of elongation of a $200-$mm$-$long region just before it fractures if failure occurs at $=0\mathrm{.}12$ mm $/$ mm$.$

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