A spiral loop has inner radius 10 cm and outer radius 20 cm and carries current 1A in each turn. The total number of turn in loop is 100. A small rectangular loop of area 2 $c{m}^2$ carries current 0.05 A is placed at the centre of loop. If magnitude of potential energy of rectangular loop is  $\frac{{\mu }_0\ln 2}{x}J$.Calculate  $x$.