A wire of length L and radius r is clamped rigidly at one end. When the other end of the wire is pulled by a force F, its length increases by 5 cm.…

A wire of length $\displaystyle L$ and radius $\displaystyle r$ is clamped rigidly at one end. When the other end of the wire is pulled by a force F, its length increases by $\displaystyle 5$ cm. Another wire of the same material of length 4L and radius 4r is pulled by a force 4F under same conditions. The increase in length of this wire is \_\_\_\_ cm .