$\begin{array}{1 1} \Delta T_b=K_bm\;where\;K_b=M_t RT_b ^{+2}/\Delta _{vap} H_m \\ \Delta T_b=K_bm\;where\;K_b=RT_b^{+2}/M_1 \Delta _{vap} H_m \\ \Delta T_b=K_bm\;where\;K_b=M_t T_b ^{+2}/R\Delta _{vap} H_m \\ \Delta T_b=K_bm\;where\;K_b=M_t RT_b ^{+2}\Delta _{vap} H_m \end{array} $