\(\sigma = \frac{{Iateral\,strain\left( \beta \right)}}{{longitudinal\,strain\left( \alpha \right)}}\)
For material like copper, \(\sigma = 0.33\)
\(And,\,y = 3k\left( {1 - 2\sigma } \right)\)
\(Also,\frac{9}{y} = \frac{1}{k} + \frac{3}{n}\)
\(y = 2n\left( {1 + \sigma } \right)\)
\(Hence,n < y < k\)