21. A 8.0 L sample at 25 °C and 1.00 atm of pressure contains 0.5 moles of a gas. If an additional 0.75 moles of gas at the same pressure and temperature are added, what is the final total volume of the gas?
a. 20 L
b. 20 ml
c. 30 L
d. 25.5 L

22. 7.2 liters of an ideal gas are contained at 4.0 atm and 27 °C. Using the ideal gas law, calculate how many moles of this gas are present.
a. 22 mol
b. 1.2 L
c. 2.1 mol
d. 1.2 mol

What's is the best choice. Please help!

Additional Requirements 
Level of Detail: Only answer needed