Triathlete Dan runs along a 2-mile stretch of river and then swims back along the same route. If Dan runs at a rate of 8 miles per hour and swims at a rate of 6 miles per hour, what is his average rate for the entire trip in miles per minute?  Select
A) 1 / 9  B) 2 / 15  C) 3 / 15  D) 1 / 4  E) 3 / 8

Rationale: "dan travels 4 miles round trip . running part : ( 2 / 8 = 1 / 4 * 60 = 15 minutes ) swimming part : ( 2 / 6 = 1 / 3 * 60 = 20 minutes ) 4 miles in ( 15 + 20 ) minutes 4 / 35 = 1 / 9 mile per minute answer : 1 / 9 mile per minute"
Answer: A