ommy was walking at a rate of 4

miles

hour

at noon and at 12:30 pm he was walking at a brisk rate of 6

miles

hour

. Two hours later Tommy was walking at a leisurely rate of 2

miles

hour

. What was Tommy's acceleration between noon and 12:30 pm?

A) -4

miles

hr2

B) -2

miles

hr2

C) 2

miles

hr2

D) 4

miles

hr2