The answer is B. 8.3x10^3 kPa. The partial pressure of a specificĀ gas in a gas mixture is equivalent to product of its mole fraction and total pressure of the mixture. Since it was stated that the mixture is 10% oxygen, 50% helium, and the rest nitrogen, it can be determined that nitrogen is 40% of the mixture. So 40% of 2.07x10^4 kPa isĀ 8.3x10^3 kPa.