Answer
$c_{2}\approx2.148\cdot 10^{8}$ meters per second.
Work Step by Step
$c_{2}=\frac{c_{1}\sin(\theta_{2})}{\sin(\theta_{1})}$
$c_{2}=\frac{3\cdot 10^{8}\sin(31^{\circ})}{\sin(46^{\circ})}$
$c_{2}\approx2.148\cdot 10^{8}$ meters per second.