i$.$ Label the points lettered A$,$ B and D$.$ explain what happens to the specimen in the regions OA$,$BC$,$CD and DE $.[10]$ii$.$ Briefly give an account of why stress curve OABCE $\text{'}$ is higher than curve OABCDE $.[1]$c$)$ The wire is made of a copper alloy and has a stress$-$strain relationship as shown in the graph below. Estimate the yield stress of the wire using the offset line with a strain of $0\mathrm{.}002.[2]$