Answer:
3 and and half minutes--> 7ft
Explanation:
If it travels 24 inches aka 2ft per minute
then it has to travel 12 inches aka 1ft in 30secs
SO
3mins and 30secs to travel 7ft
24inches--- 2ft---- per minute
4ft--- 2 mins
6ft---- 3mins
7ft--- 3minutes and 30 seconds