Steve goes to school 350 miles from home. Driving home one weekend, he travels 70 mph for the first 140 miles, and then slows to 30 mph for 30 miles of a construction zone. He drives the last 180 miles at 60 mph. How long did it take Steve to get home?
A. 2 hr.
B. 4 hr.
C. 6 hr.
D. 8 hr.