Task: Question Answering
Input (English): Problem: two pipes can fill the cistern in 10 hr and 12 hr respectively, while the third empty it in 30 hr. if all pipes are opened simultaneously, then the cistern will be filled in
Options: a. 6.67 hr, b. 8 hr, c. 8.5 hr, d. 10 hr, e. none of these
Output (English): a