This is solved on the Nav Computer, WCA
is another term for drift except that, while drift is usually expressed as port
and starboard or left and right, the WCA uses + and -. The mnemonic for
conversion is Port Plus.
On the CRP5 or similar use the wind face and the high speed scale.
Rotate the inner scale to put 340º at the top and mark the wind
cross 30kt down from the centre ring.
Place the TAS, 420kt under the centre ring.
Put the course (track) of 017º initially at the top, read an
initial drift of 2.5º right.
Rotate the inner scale 2.5º to the right to lay off the drift
then, finally, read a heading of 015ºT, a drift of 2º right and a groundspeed
of 396kt. The WCA is –2º,