Albert walks 4/5 of a mile in 5/12 of an hour. Which expression can be used to calculate his unit rate in miles per hour?
A. 4/5 - 5/12
B. 5/12 x 4/5
C. 5/12/4/5
D. 4/5/5/12
A. 4/5 - 5/12
B. 5/12 x 4/5
C. 5/12/4/5
D. 4/5/5/12