A car, during its entire journey of 5 hours, travels the first 45 minutes at a certain speed, the next 75 minutes at a speed of 85 km/h, and the last 3 hours at a speed of 70 km/h. During its entire journey, the average speed of the car is found to be 73 km/h.
What is the speed (in km/h) of the car during the first 45 minutes?

A

65

B

68

C

62

D

72