a boat travels at 16 knots
1st leg: 6hr @ S63W
2nd leg: 4hr @ N10E
find time and bearing back to port
6hr @ S63W = 96@S63W = (-85.53,-43.58)
4hr @ N10E = 64@N10E = (11.11,63.03)
add them up to get (-74.42,19.45) = 76.92@N75W
So,
the bearing of the port on return is S75E.
Time to port is 76.92/16 = 4.8 hr