Answer: 721.1 km/h, at 86.6 degrees north of west
Step-by-step explanation:
The magnitude of the velocity of the plane can be found by calculating the resultant of the two velocities:

The direction can be found as follows:

where 720 km/h represents the velocity towards north, while 40 km/h represents the velocity towards west, so the angle is measured with respect to east. Therefore:
the direction is
north of west