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