In this task, you need to provide the correct option for a given problem from the provided options.

Problem: in a certain kindergarten , every child has got either a dog or a cat or both . 18 children have got dogs only and 6 children have got both dogs and cats . if there are 30 children in the kindergarten , how many of them have cats ?
Options: a ) 6 , b ) 12 , c ) 14 , d ) 16 , e ) 20
b