Answer
a). $314$ million km,
b). $150$ million km.
Work Step by Step
a). In 4 months, earth will travel $120^{\circ}$
So, arc length $=\frac{2}{3}\times\frac{22}{7}\times 150$ million km=$314$ million km
b). By sine law,
if required distance = d
then, $\frac{d}{sin120^{\circ}}=\frac{r}{sin60^{\circ}}$
$dsin60^{\circ}=150sin120^{\circ} $million km
So, $d=150$ million km.
