The distance from City A to City B is 180 miles. While driving from City A to City B, Cara drives at a constant speed of 30 miles per hour. Dan leaves City A 120 minutes after Cara. What is the minimum constant speed in miles per hour that Dan must exceed in order to arrive in City B before Cara?
Choose the correct choice.
A) 42
B) 45
C) 46
D) 48
E) 50

Rationale: "the time it takes cara to drive to city b is 180 / 30 = 6 hours . dan needs to take less than 4 hours for the trip . dan needs to exceed a constant speed of 180 / 4 = 45 miles per hour . the answer is b ."
Answer: B