A mechanic can install carburetors in 3 cars every 4 hours. At that rate, how long will it take the mechanic to install carburetors in 5 cars?
A. 6 hr. 20 min.
B. 6 hr. 40 min.
C. 7 hr. 15 min.
D. 7 hr. 30 min.
E. 7 hr. 45 min.