This is what I can make sense of. Unable to think beyond it.
Conversion angle=0.5*dlong *sin mean lat
=0.5*10*sin56
=4.145 degree(or 4 degrees)
so, initial GC track at waypoint 3(or 20 W)=(270+4)= 274 degrees
Now drift = angular difference between track and heading
HDG= 270 degrees (therfore drift= 4 degrees SB)
Similarly GC track at waypoint 4 (or 30 W) = (270-4)= 266 degrees
Here drift = 4 degrees port (assuming hdg remains 270)