In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: three pipes , a , b , & c are attached to a tank . a & b can fill it in 20 & 30 minutes respectively while c can empty it in 15 minutes . if a , b & c are kept open successively for 4 minute each , how soon will the tank be filled ? 
Options: a ) 2 hours , b ) 12 hours , c ) 3 hours , d ) 5 hours , e ) 6 hours
b

Problem: a can do a work in 4 days . b can do the same work in 6 days . both a & b together will finish the work and they got $ 1000 from that work . find their shares ? 
Options: a ) 600,400 , b ) 500,500 , c ) 300,700 , d ) 800,200 , e ) 550,450
a

Problem: 39 persons can repair a road in 12 days , working 5 hours a day . in how many days will 30 persons , working 3 hours a day , complete the work ? 
Options: a ) 10 , b ) 26 , c ) 14 , d ) 15 , e ) 16

b