OK, well angle ARC is 360° × (3000/24902)

The angle ARE is half that.

The length RE is therefore cos(360° × (3000/24902) /2 ) × 6,378km

RE = cos(21.685°) × 6,378km = 5,927 km

AE = sin(21.685°) × 6,378km = 2,357 km

So distance ED = (6,378-5,927) + 830 = 1,281 km

We now know AE and ED, so the angle from that is:

tan-¹(2,357/1,281) = 61.5°, and you need to double that to 123° --> ANSWER = 123°

There may be an easier way to get there, I just went about soloving triangles till I got there.