Ammonium nitrate decomposes to yield nitrogen gas

Ammonium nitrate decomposes to yield nitrogen gas, water, and oxygen gas in the following reaction:

2NH4NO3→2N2+O2+4H2O

a. How many moles of nitrogen gas are produced when 36.0 g of NH4NO3 reacts?
b. If 7.35 mol of H2O are produced in this reaction, what mass of $$\mathrm { NH } _ { 4 } \mathrm { NO } _ { 3 }$ reacted?