[填空题]
The current through the y7 ,(7 f6zc2 jeyzwkrbk ap2z5l6 m/9,bskft oh/ n(nu$20-\Omega$ resistor in (Fig. Below) does not change whether the two switches $S_1$ and $S_2$ are both open or both closed. Use this clue to determine the value of the unknown resistance R. $\Omega$
