How many grams of hydrogen gas must be burned...?

Hydrogen is burned in oxygen to release heat. How many grams of hydrogen gas must be burned to release enough heat to warm a 50.0 g block of iron, giving 8 mol of water?
2 H2(g) + O2(g) → 2 H2O(g) ΔH = −484 kJ
Iron has a specific heat of 0.449 J/(g·°C).
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