A mixture of NH3(g) and N2H4(g) is placed in a sealed container at 320 K. The total pressure is 0.51 atm. The container is heated to 1200 K at which time both substances decompose completely according to the equations 2NH3(g)→N2(g)+3H2(g); N2H4(g)→N2(g)+2H2(g). After decomposition is complete the total pressure at 1200 K is found to be 4.5 atm. Find the percent (by volume) of N2H4(g) in the original mixture.