Taps A and B can fill a bucket in 15 minutes and 30 minutes respectively. If both are opened and A is closed after 4 minutes, how much further time would it take for B to fill the bucket?	Options.
A) 19 mins.
B) 15 mins.
C) 18 mins.
D) 16 mins.
E) 17 mins.
Explanation:   Part filled in 3 minutes =   4∗(1/15+1/30)=4∗1/10=2/5   Remaining part =1−2/5=3/5   =&gt;1/30:3/5=1:X   =&gt;X=18   =&gt;X=18 mins.   So it will take further 18 mins to fill the bucket.   Option 18 mins.
<result>C</result>
Taps A and B can fill a bucket in 15 minutes and 30 minutes respectively. If both are opened and A is closed after 4 minutes, how much further time would it take for B to fill the bucket?