One pump drains one-half of a pond in 5 hours, and then a second pump starts draining the pond. The two pumps working together finish emptying the pond in one-half hour. How long would it take the second pump to drain the pond if it had to do the job alone?	Select:
A) 1 hour
B) 1.2 hour
C) 3 hours
D) 5 hours
E) 1.1 hours

Rationale: "the tricky part here , i believed is one half hour = 1 / 2 . then everything would be easy . we have the 1 st pump working rate / hour = 1 / 2 : 5 = 1 / 10 working rate of 2 pumps : 1 / 2 : 1 / 2 = 1 . working rate of 2 nd pump : 1 - 1 / 10 = 9 / 10 - - > time taken for the 2 nd pump to finish : 1 : 9 / 10 = 10 / 9 = 1.1 hours . e"
Answer: E