Please help

1. A certain car tire has a volume of 15.0 L. On a day where the temperature is 25.0C, the pressure inside the tire was measured at 2.20 atm. The mole fraction of oxygen in the air inside the tire is 0.212. Find the total number of moles of oxygen inside the tire. Give your answer to the correct number of significant figures, and make sure it is accurate to that number of figures.

2. What is the most probable speed of Argon gas atoms at 30.0C?