Answer
Please see the work below.
Work Step by Step
a. We know that the required chemical equation is
$N_2H_4(l)+\frac{1}{2}N_2O_4(l)\rightarrow \frac{3}{2}N_2(g)+2H_2O$ so $\Delta H=-524.5KJ$
b. The required thermochemical equation is
$4H_2O(g)+3N_2(g)\rightarrow 2N_2H_4(l)+N_2O_4(l)$ so $\Delta H=1049KJ$
