a
\(\frac{\left( T _{ B }\right)_{ x }}{\left( T _{ B }\right)_{ y }}=\frac{2}{1} \quad \frac{(\Delta H )_{ x }}{(\Delta H )_{ y }}=\frac{1}{2}\)

\(\frac{\left(\Delta T _{ B }\right)_{ x }}{\left(\Delta T _{ B }\right)_{ y }}= m =\frac{\left( K _{ B }\right)_{ x } \times \text { molality }}{\left( K _{ B }\right)_{ y } \times \text { molality }}\)

\(=\frac{( T \cdot B )_{ x }^2}{( T \cdot B )_{ y }^2} \times \frac{\Delta H _{ y }}{\left(\Delta H _{ x }\right.}=(2)^2 \times 2=8\)