Aspace probe is launched from earth, headed for deep space. at a distance of 15,000 miles from the earth center, the gravitational force on it is 800 lb.

200 lb

Explanation:

The rest of the question is written below:

What is the size of the force when it is at 30,000 miles from the Earth's center?

According to Newton's Universal Law of Gravitation:

 (1)

Where:

 is the gravitational force

is the gravitational constant

 is the mass of the Earth

is the mass of the probe

is the distance between the Earth and the probe

In this case we have:

  gravitational force when the distance is and we have to find   gravitational force when the distance is .

Then:

 (2)

 (3)

Dividing (2) by (3):

 (4)

Simplifying:

 (5)

Finding :

 (6)

 (7)

Finally:

wavelength variability is the right one