1 AU means 1 astronomical unit or the aproximate distance from the earth to the sun
1AU=149597870.7 kiometers
1 billion=1,000,000,000
600 billion=600,000,000,000
x times 1AU=600,000,000,000
x times 149597870.7=600,000,000,000
solve for x
divide both sides by 149597870.7
x=4010.75
so aprox 4011 AU's
