$6.$ If a brass specimen having a rectangular cross section of dimensions $\backslash (12\mathrm{.}7\backslash$mathrm$\{$~mm$\}\backslash$times $6\mathrm{.}4\backslash$mathrm$\{$~mm$\}\backslash )$ and $120$ mm long is pulled in tension.

a$)$ Compute the final length of the specimen with a load of $15000$ N $($load applied$)$

b$)$ Compute the final length of the specimen when the same load is released.

c$)$ Compute the final specimen length when the load is increased to $32\mathrm{.}5$ kN

d$)$ Compute the final specimen length when the load is increased to $32\mathrm{.}5$ kN and then released.