A Force Of $20 \mathrm{~N}$ Is Applied to a Wire with an Unstretched Length Of with an Unstretched

A force of $20 \mathrm{~N}$ is applied to a wire with an unstretched length of $2.5 \mathrm{~m}$ . The wire gets $2.00 \mathrm{~mm}$ longer. The strain in the wire is

A) $10 \times 10^{-4}$ .
B) $8.0 \times 10^{-4}$ .
C) $4.0 \times 10^{-4}$ .
D) $6.0 \times 10^{-4}$
E) $2.0 \times 10^{-4}$