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 \( 5 \,\text{cm} \). 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 ______ \( \text{cm} \).
