Mass of the sun =2×1030kg=Ms
Mass of the earth =6×1024kg=Me
orbital radius =1.5×1011m
Mass of the rocket =m
Now,lets think the distance is r
Let's think that x is the distance from earth's center where the gravitational force on the rocket is zero.
gravitational force of the earth =GmMe/x2
Gravitational force of the sun =GmMs/(r−x2)
Using Newton's law,
See the picture above...
Now we can say that the distance is 2.59×108.