Given the following data

$NH3(g)\frac{1}{2}N2(g)+\frac{3}{2}H2(g),H=46kJ$

$2H2(g)+O2(g)2H2O(g),H=-484kJ$

Calculate $H$ for the reaction

$2N2(g)+6H2O(g)3O2(g)+4NH3(g)$

a$)1268kJ$

b$)1636kJ$

c$)-1636kJ$

d$)-438kJ$