Tricky question
Work done is the change in potential energy.
1 MJ = 1x10^6 J
Chenge in EP = (-Gm1m2)/(20000x10^3) - (-Gm1m2)/(10000x10^3)
1x10^6 = (-Gm1m2+Gm1m2)/(20000x10^3)
2x10^13 = Gm1m2
To move object from 20000 km to 80000 km
-Gm1m2/(80000x10^3) - (-Gm1m2)/(20000x10^3) (Now sub...