Gravitation Field Question / Conservation of Energy A level EDEXCEL physics

Theres this question im stuck on, if anyone could help me that would be great. Ive tried atleast 10 times. Ive used the markscheme to try and help me get the answer, Ive used chatgpt, but I cant get the answer on the markscheme:
In 2015 the Messenger spacecraft crashed into the surface of the planet Mercury after four
years in orbit observing the surface of Mercury.
Messenger's orbit was highly elliptical, varying between 200 km and 15 000 km above the
surface of Mercury. Messenger completed one full orbit every 12 hours.
mass of Messenger spacecraft = 565 kg
mass of planet Mercury = 3.30 × 1023 kg
radius of planet Mercury = 2430 km
Calculate the velocity an object would have as it reached the surface of Mercury if it was
released from Messenger's maximum orbital height.
Assume the object is released from rest and that Mercury has no atmosphere.
The main thing ive tried is GPE max (so maximum distance from mercury) = gpe min (minumum distance from mercury) + KE
But im not getting 3948 m/s, which it says is the right answer

Theres this question im stuck on, if anyone could help me that would be great. Ive tried atleast 10 times. Ive used the markscheme to try and help me get the answer, Ive used chatgpt, but I cant get the answer on the markscheme:

In 2015 the Messenger spacecraft crashed into the surface of the planet Mercury after four
years in orbit observing the surface of Mercury.
Messenger's orbit was highly elliptical, varying between 200 km and 15 000 km above the
surface of Mercury. Messenger completed one full orbit every 12 hours.

mass of Messenger spacecraft = 565 kg

mass of planet Mercury = 3.30 × 1023 kg

radius of planet Mercury = 2430 km

Calculate the velocity an object would have as it reached the surface of Mercury if it was
released from Messenger's maximum orbital height.
Assume the object is released from rest and that Mercury has no atmosphere.

The main thing ive tried is GPE max (so maximum distance from mercury) = gpe min (minumum distance from mercury) + KE
But im not getting 3948 m/s, which it says is the right answer

It does sound as though you had the right idea.
It asks what velocity an object would have if dropped from the maximum orbital height of the spacecraft- you aren’t calculating the velocity of the spacecraft itself. As such, you presumably would have to pick the mass of the object as they haven’t actually specified what it is in the question.
One thing is for certain and that is irrespective of the chosen value of m, ΔEp will be the same:
Max height = 15000 km + 2430 km = 1.743 x 10^7 m
Min height = 2430 km = 2.43 x 10^6 m
Ep (max h) = GM/(1.743 x 10^7) = 1.263 x 10^6 J
Ep (min h) = GM/(2.43 x 10^6) = 9.058 x 10^6 J
ΔEp = 7.795 x 10^6 J
(Recall that G is 6.67 x 10^-11 N m^2 kg^-2 and M = 3.30 x 10^23 kg)
Equating this to KE:
1/2 x m x v^2 = 7.795 x 10^6
v = sqrt(1.559 x 10^7 / m)
If we assume the object has a mass of 1 kg, then we do get an answer of 3948 m/s. I personally think this was a terrible question and if they wanted this answer specifically they should have told you the mass of the object itself