Lexy used the formula shown to calculate the force of gravity on a space shuttle.

Fg = GStartFraction (3 times 10 Superscript 5 Baseline kilograms) (6 times 10 Superscript 24 Baseline kilograms) over [(6.4 times 10 Superscript 6 Baseline m) + (1.8 times 10 Superscript 5 Baseline m)] Superscript 2 EndFraction

What does 3 × 105 kg represent?

the difference between Earth’s mass and the space shuttle’s mass
the sum of Earth’s mass and the space shuttle’s mass
the mass of Earth
the mass of the space shuttle