9514 1404 393
Answer:
1604 m
Explanation:
The relevant trig relation is ...
Sin = Opposite/Hypotenuse
Here, the "opposite" is the elevation of point B above point A, and the "hypotenuse" is the length of the railway. Then the total height of point B is ...
B = 856 + 864·sin(120°)
B = 856 +864(√3)/2 = 856 +432√3 ≈ 1604.246
The height of the train at point B is about 1604 m above sea level.