A mixture of three noble gases has a total pressure of 1 point 2 5 atm. The individual pressures exerted by neon and argon are 0 point 6 8 atm and 0 point 3 5 atm, respectively. What is the partial pressure of the third gas, helium? Use cap p sub cap t is equal to cap p sub 1 plus cap p sub 2 plus cap p sub 3 plus dot dot dot cap p sub n