#### Answer

a). $(4)$
b). increase 1.4 times.

#### Work Step by Step

a). Intensity is inversely proportional to square of distance.
So, $\frac{I_{1}}{I_{2}}=\frac{R_{2}^{2}}{R_{1}^{2}}$
$\frac{I_{1}}{I_{2}}=\frac{(3R)^{2}}{R^{2}}=9$
Thus, $I_{2}=\frac{1}{9}I_{1}$
So, (4) is the answer.
b). $\frac{I_{1}}{I_{2}}=\frac{R_{2}^{2}}{R_{1}^{2}}=2$
$R_{2}=\sqrt 2\times R_{1}$
So, the distance is increased 1.4 times.