N₂ (g) + 3H₂(g) → 2NH3(g)

If 18.2 kg N₂ is mixed with 4.50 kg H₂, and 19.8 kg of NH3 is collected.

(a) Which reactant is the limiting reagent?
(b) How many kilograms of the excess reagent left?
(c) What is the percent yield of NH3