Feruza, you said:
E contradicts the statement. There is a new info on B, but it is ok for strengthen the conclusion type CR question.
But E does not contradict the statement! The argument says people feel better with old drug after 3 days and stop taking it, but the infection is not totally killed yet, so they get reinfected.
Now, E says that with new drug people feel better after 3 days, which means that they will keep taking the drug for all 3 days. Since it takes 3 days for a new drug to kill the bacteria, the infection is totally killed and reinfection does not occur.
As for the B, cost does not affect the efficiency of the new drug.