Initial Position 60N 030W
3600 NM going south equals 60 deg (1 NM=60 deg on a meridian which is a great circle)
second position 000 030W
3600 NM going east equals 60 deg (1 NM= 60 deg on the equator which is a great circle)
third position 000 030E
3600 NM going north equals 60 deg (1 NM=60 deg on a meridian which is a great circle)
forth position 60N 030E
3600 NM going west equals this time 120 deg
(e=G cosL=3600 that means g=e/cosL=3600/cos60=7200'=120deg)
Final position is 60N 090W
I guess the answer on the book is not correct.