A plane travels 350 km south along a straight path with an average velocity of 125 km/h to the south. The plane has a 30 minute layover, and then travels 220 km south with an average velocity of 115 km/h to the south. What is the average velocity for the trip?
a.120 km/hr to the south
b.110 km/hr to the south
c. 121 km/hr to the south
d. need more information