A laboratory cylinder contains a mixture of three ideal gases at 25 °C. The partial pressures are 215 torr O₂, 102 torr N₂, and 88 torr Ar. What is the total pressure of the mixture, expressed in atmospheres?
a) 1.88 atm
b) 0.405 atm
c) 0.533 atm
d) 0.283 atm