The answer is 0 Newtons
This is because of a key word in the question: “constant”
When we say something has a constant speed, that means that its acceleration is 0.
Using the equation derived for Newton’s 2nd law, we see that F=ma
Force = mass x acceleration
If acceleration, a, equals 0, then when we multiply our mass times acceleration 0
F=m(0)
Anything times zero equals zero
So, F=0