each group take 5 mins to do 2yds
2 groups so in 5 mins, 4 yards gets cleaned
how many yards per mile is 1760
2 miles=2*1760=3520
find how many times of the 5 mins they have to clean (remember 4 yds per 5 mins)
3520/4=880
that means 880 times 5mins=4400mins=73hrs and 20mins