Task: Question Answering
Input (English): Problem: two pipes a and b can fill a tank in 24 minutes and 32 minutes respectively. if both the pipes are opened simultaneously, after how much time should b be closed so that the tank is full in 18 minutes ?
Options: a. 7 minute, b. 9 minute, c. 10 minute, d. 8 minute, e. 11 minute
Output (English): d