A construction worker needs to determine the volume of a sandpile in a construction yard, as shown. -A line along the surface of the sandpile from the ground to the top of the sandpile makes a 40° angle with the ground at point R.
- The length of the slant side of the sandpile, line RT, from the ground to the top of the sandpile is 20 meters .

What is the volume of this sand pile to the nearest cubic meter? Show your answer and explain how you determine your answer.