Please how do i get an answer to this answer that goes like this

Question

a wire of length 5.0m and diameter 2.0cm extends by 0.25mm when a force of 50n was used on its end. Calculate
(i) stress
(ii) strain in the wire (pi=3.142)

Answer 1

stress=force/area=50/(PI*.02^2) N/m^2

strain=extension/length=2.5E-4/5
= .5E-4