Q: 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: a can do a work in 7 days b in 12 days and c in 5 days . if they work on it together then in how many days required to complete the work ?
Options: a ) 420 / 177 , b ) 420 / 179 , c ) 410 / 87 , d ) 90 / 14 , e ) 77 / 56
A:
b