A wire of length 10 cm and radius $\sqrt 7 \times {10^{ - 4}}\;{\rm{m}}$ connected across the right gap of a meter bridge. When a resistance of $4.5\Omega $ is connected on the left gap by using a resistance box, the balance length is found to be at 60 cm from the left end. If the resistivity of the wire is ${\rm{R}} \times {10^{ - 7}}\Omega \;{\rm{m}}$, then value of R is :