In a meter bridge (shown in the figure), the null point is found at a distance of 33.7 cm from A. If now a resistance of 12 $\Omega$ is connected in parallel with S, the null point occurs at 51.9 cm. The values of R and S are respectively:

$1. 13.5 \Omega , 6.86 \Omega$
$2. 13.5 \Omega , 13.5 \Omega$
$3. 6.86 \Omega , 6.86 \Omega$
$4. 6.86 \Omega , 13.5 \Omega$

A resistance of $R \Omega$ draws current from a potentiometer. The potentiometer has a total resistance $R_0 \Omega$  (as shown in the figure). A voltage V is supplied to the potentiometer. What is the voltage across R when the sliding contact is in the middle of the potentiometer?

$1. \frac{2VR}{R_0+4R}$
$2. \frac{VR}{R_0+4R}$
$3. \frac{2VR}{R_0+2R}$
$4. \frac{VR}{R_0+2R}$