Physics: Principles with Applications (7th Edition)

$3.0 \times 10^{-5}m$
Use the definition of strain. $$\Delta \mathcal{l}=(\mathcal{l}_o)(strain)$$ $$=(8.6m)( 3.5 \times 10^{-6})=3.0 \times 10^{-5}m$$