According to the Gravity model (Reilly's law), the trade area boundary between two competing retail centers is a function of their size and the distance between them. Suppose that the driving time between Shopping Center A and B is 20 minutes. Moreover, Center A's size is 400,000 square feet and Center B's size is 100,000 square feet. Based on the Gravity model, how far is the distance (measured in driving time by minute) between Center B and the break point of the trade areas(or the market boundary line)?

5.67 minutes

12.67 minutes

6.67 minutes

8.87 minutes