An unusual question as it has been asked. Questions with positions on different latitudes usually state that the highest track (or vertex) occurs at a particular longitude.
At the vertex the GCT must be either 270 or 090, then you can use convergency (conversation angle not available) between the given vertex longitude and wherever they want the GCT measured.
Once you have done a couple these are relatively straightforward.
For this question I drew an accurate scaled polar/circle diagram and got GCT at A 190 GCT at B 340, but the diagram is too complicated to show & explain here.
I wouldn't waste too much time on these type of questions, also not sure your source of questions is entirely reliable, been some strange wording along with an incorrect answer before.