$3.$ In a creep test, a material with $\backslash (\backslash$mathrm$\{$E$\}=600\backslash$mathrm$\{$MPa$\}\backslash )$ is initially loaded with a stress $\backslash (\backslash$sigma$\_\{0\}\backslash ).$ Half an hour after the initial loading, the strain in the material is measured to be $0\mathrm{.}123,$ and after another hour, it is found to be $0\mathrm{.}234.$

a$)$ What will be the strain in material $3$ hours after the initial loading?

b$)$ How much time did it take for the strain to reach a value of $0\mathrm{.}001?$