$OA+OB+OC+OD=5+\sqrt{125}+\sqrt{125}+5=10+2\sqrt{125}=10+10\sqrt{5}$  $OE=2OA$  $OB=\sqrt{O{{E}^{2}}+E{{B}^{2}}}=\sqrt{100+25}=\sqrt{125}=OC=OB$  $O{{B}^{2}}=100+25=125\Rightarrow OB=\sqrt{125}=5\sqrt{5}$