You drive 6.0 km at 50 km/h and then another 6.0 km at 90 km/h. Your average speed over the 12 km drive will be
A) greater than 70 km/h.
B) exactly 38 km/h.
C) less than 70 km/h.
D) equal to 70 km/h.
E) It cannot be determined from the information given because we must also know directions traveled.