Two resistors \( 2\,\Omega \) and \( 3\,\Omega \) are connected in the gaps of bridge as shown in figure. The null point is obtained with the contact of jockey at some point on wire \( XY \). When an unknown resistor is connected in parallel with \( 3\,\Omega \) resistor, the null point is shifted by \( 22.5 \,\text{cm} \) toward \( Y \). The resistance of unknown resistor is ______ \( \Omega \).
