The helium-filled balloon in Example 15.2 contained n = 1.1 moles of helium atoms at roo...

The helium-filled balloon in Example 15.2 contained n = 1.1 moles of helium atoms at room temperature and a pressure (twice atmospheric pressure). Atoms are added to the balloon so that the pressure doubles to while the temperature and volume are kept fixed. Is the number of moles in the balloon (a) 1.1 moles, (b) 2.2 moles, (c) 4.4 moles, or (d) 0.55 mole?

(reference example 15.2)