Detailed Instructions: In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Q: Problem: a boat traveled upstream 90 miles at an average speed of ( v - 3 ) miles per hour and then traveled the same distance downstream at an average speed of ( v + 3 ) miles per hour . if the trip upstream took a half hour longer than the trip downstream , then how many hours did it take the boat to travel downstream ?
Options: a ) 2.5 , b ) 2.4 , c ) 2.3 , d ) 2.2 , e ) 2.1
A:
a