What is helpful is not underestimated, and what is not helpful is a waste of time.
We can infer that...
What is underestimated is a waste of time.
What is not a waste of time is helpful.
Hmmm... we can validly infer both. The first answer requires a chain of inference, but is a valid inference and is the credited choice and even needs the second inference to fill the first sufficient condition of the chain. The second is the contrapositive of the second phrase of the stimulus and is a valid inference but is not credited. Not H--> W ---> Not W----> H.
I'm not sure how long this question has been up, but it needs fixing.
