(a) $\frac{T_{A}}{M_{A}} = 4\frac{T_{B}}{M_{B}} \Rightarrow \sqrt{\frac{T_{A}}{M_{A}}} = 2\sqrt{\frac{T_{B}}{M_{B}}}$
$\Rightarrow \sqrt{\frac{3RT_{A}}{M_{A}}} = 2\sqrt{\frac{3RT}{M_{B}}} \Rightarrow C_{A} = 2C_{B} \Rightarrow \frac{C_{A}}{C_{B}} = 2$