A Truck Driver Started for His Destination at an Average $4.7 \mathrm{hr}$

Multiple Choice

A truck driver started for his destination at an average speed of 70 miles per hour. Once snow began to fall, he had to drop his speed to 40 miles per hour. It took the driver 14 hours to reach his destination, which was 707 miles away. How many hours after the driver started did the snow begin to fall?

A) after $4.7 \mathrm{hr}$
B) after $4.9 \mathrm{hr}$
C) after $9.1 \mathrm{hr}$
D) after $9.3 \mathrm{hr}$