Answer:
The total pressure of the gas mixture is given by the sum of the partial pressures of each gas:
Ptotal = Pn + Pne + Pkr
Substituting the given values:
Ptotal = 240 mmHg + 52 mmHg + 419 mmHg
Ptotal = 711 mmHg
Therefore, the total pressure of the gas mixture is 711 mmHg.