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: twelve machines , each working at the same constant rate , together can complete a certain job in 6 days . how many additional machines , each working at the same constant rate , will be needed to complete the job in 3 days ? 
Options: a ) 14 , b ) 12 , c ) 15 , d ) 16 , e ) 18
b

Problem: the population of a bacteria colony doubles every day . if it was started 8 days ago with 3 bacteria and each bacteria lives for 12 days , how large is the colony today ? 
Options: a ) 512 , b ) 768 , c ) 13122 , d ) 2048 , e ) 4096
c

Problem: with both inlets open , a water tank will be filled with water in 52 minutes . the first inlet alone would fill the tank in 2 hours . if in every minutes the second inlet admits 50 cubic meters of water than the first , what is the capacity of the tank ? 
Options: a ) 9,000 , b ) 10,500 , c ) 11,750 , d ) 17,500 , e ) 19,500

e