If shawn cleans the backyard alone, he can finish it in 1 hour. meanwhile, if frank cleans the backyard alone, he can finish it in 1.5 hours. suppose that shawn and frank decided to help each other cleaning the backyard. how long can shawn and frank finish cleaning the backyard?
a. 3/5 hour
b. 2/5 hour
c. 1/5 hour
d. 5/3 hour
