Assuming pressure and temperature remain constant, what happens to the volume of a gas if the number of moles of gas is increased (gas is added)?

Question

1) Remains the same
2) Cannot be determined
3) Increases
4) Decreases

Answer 1

PV = nRT . R and T are constants.
P stays same.
R stays same
T stays same
If n is doubled what must happen to V.
Check my thinking.