Ammonia (nh3) burns in air to form nitrogen dioxide and water. calculate grams of nitrogen dioxide produced if 4.0 grams of ammonia are consumed

The balanced equation for the above reaction is;
4NH₃ + 7O₂  --> 4NO₂  + 6H₂O
stoichiometry of NH₃ to NO₂ is 4:4
the number of NH₃ moles consumed are - 4.0 g / 17 g/mol = 0.24 mol
number of NH₃ moles reacted are equivalent to number of NO₂ moles formed 
therefore number of NO₂ moles formed - 0.24 mol x 46 g/mol = 11.04 g
mass of NO₂ formed is 11.04 g

The answer is c) pyrite