One mile high,
The actual would be -1.3 for 5N, the question posed here is asking for the difference so the difference from 5S (1.3) to 5N (-1.3) would be -2.6 = -1.3 - 1.3 and not 0 = 1.3 - 1.3.
I can't see how there wouldn't be any drift at 5N or 5S as the equation the CAA expect you to use is 15*sin(lat) for Earth Rate.