About how much air does Rasmina have to blow into a spherical ballon into order to inflate it to a diameter of 2 feet

If the diameter is 2 feet, the radius is 1 foot.

The formula for volume of a sphere is:

Volume = (4/3) * pi * (radius) ^3. (in units of foot^3).

If radius = 1 foot then:

Volume = (4/3) pi = 4.1887902 (foot^3).