Very Difficult Calc Question!

Our professor gave us this one question for "bonus" marks last week and nobody got it. Just wondering how to solve this:

If two masses m1 and m2 (in kg) are a distance d (in m) apart, then the force F (in N) of gravity is F = Gm1 m2 /d2 , where G = 6.67×10^-11 Nm2 /kg2 . If the mass of the Earth is 5.97×10^24 kg and the radius of the Earth is 6380 km, calculate the work required (in J) to send a mass of 1 kg to the edge of the universe. Be careful with units and note that this will involve an improper integral.