20 beavers, working together in a constant pace, can build a dam in 3 hours. How many B hours will it take 12 beavers that work at the same pace, to build the same dam?  Choose the correct choice from the following answers.
A) 2 .  B) 4 .  C) b = 5 .  D) b = 6 .  E) b = 8 .

Rationale: "c . 5 hrs if there were 10 beavers it could have taken double b = 6 hrs . . so closest to that option is 5 . c"
Answer: C