The difference between the rhumb-line track and the great circle track at either end is the conversion angle (C.A.), which is half convergence. Really you must use Earth convergence, not chart convergence, as this would concern a straight line on a chart, not a great circle. In this case they are actually the same, so C.A. is 6 degrees.
Then we need to know which end is in question - the great-circle track varies. The rhumb line will be closer to the equator than the great circle, so at A the great-circle track is greater than the rhumb-line track. This would make it 320(T). At B the track would be less, at 308 degrees.
Send Clowns
General Navigation Instructor
BCFT