The resistance per centimeter of a meter bridge wire is \( r \), with \( X \, \Omega \) resistance in left gap. Balancing length from left end is at \( 40 \, \text{cm} \) with \( 25 \, \Omega \) resistance in right gap. Now the wire is replaced by another wire of \( 2r \) resistance per centimeter. The new balancing length for same setting will be at: