A 0.505 -in.-diameter metal bar with a 2 -in. gage length $l_0$ is subjected to a tensile test. The following measurements are made in the plastic region:
$$
\begin{array}{lcc}
\text { Force (Ib) } & \begin{array}{c}
\text { Change in Gage } \\
\text { length (in.) (A } \text { ) }
\end{array} & \begin{array}{c}
\text { Diameter } \\
\text { (in.) }
\end{array} \\
\hline 27,500 & 0.2103 & 0.4800 \\
27,000 & 0.4428 & 0.4566 \\
25,700 & 0.6997 & 0.4343
\end{array}
$$
Determine the strain-hardening exponent for the metal. Is the metal most likely to be FCC, BCC, or HCP? Explain.